Erchonia Medical MSM1-RF MSM1-RF User Manual HP3 TX working 70103

Erchonia Medical MSM1-RF HP3 TX working 70103

Contents

Transmitter design guide

HP SERIES-3 TRANSMITTER DESIGN GUIDEDE S C R IP TION:The HP-3 R F transmitter module is the third generation of the popular HP series andoffers complete compatibility and numerous enhancements over previousgenerations. Like its predecess ors, the HP -3 is designed for the cost-effective, high-performance wireless transfer of analog or digital information in the popular 902-928MHz band. All HP -3 s eries parts continue to feature eight parallel selectablechannels, but versions are also available which add s erial selection of 100 channels.T o ens ure reliable performance, the trans mitter employs F M/F S K modulation and amicroproces s or-controlled synthes ized architecture. The transmitter is pin- andfootprint-compatible with all previous generations but its overall physical size hasbeen reduced. B oth S MD and pinned packages are now available. W hen paired withan HP -3 receiver, a reliable link is created for transferring analog and digitalinformation up to 1000 ft. (under optimal conditions). Like all Linx modules, the HP -3 requires no tuning or additional R F components (except an antenna), makingintegration straightforward, even for engineers without prior R F experience.HIGH-PERFORMANCERF MODULETXM-900-HP3R evised 7/2/03FEATURES:€ 8 parallel, 100 serial (P S Versions ) User-S electable C hannels €P recision F requency S ynthesizedArchitecture€F M/F S K Modulation F or Outs tandingP erformance and Noise Immunity€ Transparent Analog/Digital Interface€High Data R ate (up to 56k)€Wide-R ange Analog C apability IncludingAudio (50Hz-28kHz)€P ower-Down and C TS F unctions€C ost-E ffective€P inned or S MD P ackaging€Wide S upply R ange (2.8-13V DC ) €E xtended Temperature R ange(-30°C to +85°C )€No P roduction Tuning or E xternal R FC omponents R equired (E xcept Antenna)€C ompatible With P revious HP S eriesModulesP A R T # DE S C R IP TIONTXM-900-HP 3-P P O HP -3 Transmitter (P INNE D 8 C H only)TXM-900-HP 3-P P S HP -3 Transmitter (P INNE D 8p /100s C H)TXM-900-HP 3-S P O HP -3 Transmitter (S MD 8 C H only)TXM-900-HP 3-S P S HP -3 Transmitter (S MD 8p /100s C H)MDE V-900-HP 3-P P S Development K it 900MHz (P inned P kg.)MDE V-900-HP 3-S P S Development K it 900MHz (S MD P kg.)ORDERING INFORMATIONAPPLICATIONS INCLUDE:€G eneral Wire E limination€Wireless Data Transfer€Wireless Analog / Audio€Home / Industrial Automation€Wireless Networks€R emote C ontrol €R emote Acces s€R emote Monitoring / Telemetry€Alarm / S ecurity S ystems€Long-R ange R FID€ MIDI Links€ Voice/Mus ic / Intercom Links
Figure 1: Performance Data TablePage 21. Over entire operating voltage range2. PDN pin low3. Serial Mode4. 100 Serial channels on PS versions only5. Does not change over 3-13 VDC supply 6. Into 50 Ohms7. Receiver will not reliably hold a DC level. See RX manual for minimum transition rate.8. Voltage specified is modulation pin voltage9. See page 15.Notes:TRANSMITTER SPECIFICATIONSABOUT THESE MEASUREMENTSThe performance parameters listed below are based on module operation at25°C from a 5V DC supply unless otherwise noted. Parameter Designation Min. Typical Max. Units NotesPOWER SUPPLYInput Voltage VCC 2.8 – 13.0 VDC –Supply Current ICC –1417mA1Power-Down Current IPDN ––15µA2TRANSMIT SECTIONTransmit Frequency Range FC902.62 – 927.62 MHz 3Center Frequency Accuracy -50 +50 kHz –Available Channels 8 (Par.) – 100 (Ser.) 4Channel Spacing – 250 – kHz –Occupied Bandwidth – 115 140 kHz –Output Power -3 0 +3 dBm 5Spurious Emissions – -45 – dBm 6Harmonic Emissions – -60 -47 dBm 6Data Bandwidth 100 – 56,000 bps 7Analog/Audio Bandwidth 50 – 28,000 Hz 7Data input:Logic low GND – 0.5 VDC –Logic high 2.8 – 5.2 VDC –Data Input Impedance – 200 – kOhms –Frequency Deviation @ 3VDC 60 70 110 kHz 8Frequency Deviation @ 5VDC 90 115 140 kHz 8ANTENNA PORTRF input impedance RIN –50–Ohms –TIMINGTransmitter Turn-on Time T1–710mSec 9Max Channel-Change Time T2–11.5mSec 9ENVIRONMENTALOperational Temperature -30 +85 °C –
Page 3Figure 2: Maximum Ratings TableAbsolute Maximum Ratings:Supply voltage Vcc, using pin 7 -0.3 to +18 VDCOperating temperature -30°C to +85°CStorage temperature -45°C to +85°CSoldering temperature +260°C for 10 sec.Any input or output pin -0.3 to Vcc *NOTE* Exceeding any of the limits of this section may lead to permanentdamage of the device. Furthermore, extended operation at these maximumratings may reduce the life or affect the function of this device.*CAUTION*This product incorporates numerous static-sensitive components.Always wear an ESD wrist strap and observe proper ESD handlingprocedures when working with this device. Failure to observe thisprecaution may result in module damage or failure.Figure 5: TX Powerup to Valid RX AnalogFigure 3: Power-Up To CTSTYPICAL PERFORMANCE GRAPHSFigure 8: Square-Wave Modulation LinearityFigure 6: Sine-Wave Modulation LinearityFigure 4: TX Powerup to Valid RX DataFigure 7: Triangle-Wave ModulationLinearityINOUTINTX VCC/PDN HighTX VCC/PDN HighRX DataDemodulated Analog Data(RX)TX CTSTX VCC/PDN HighOUTINOUT
PIN Name Equivalent CTK Description PIN #Ground50 Ohm RF OutputChannel Select 0CS0Channel Select 1/Serial Select ClockCS1Channel Select 2 /Serial Select DataClear-to-SendOutputGround/ModeVoltage Input 2.8-16VPower Down(Active Low)Digital/Analog InputSee text "Inputting Digital Data"CS2ModeCTSOutGNDRF/ANT OutCS0CS1/SS CLOCKCS2/SS DATAPDNCTSGND/MODEAnalog In/Data InVCC1313202567981112414-1921-24101234576910825K25K25K100K 160K510K 20pF50RFOutPDN430KVIN SMDPinnedN/C SMD (Only) No Connection25KPage 4PIN DESCRIPTIONFigure 9: Pin Functions and Equivalent Circuits
Page 5The transmitter is available in two package styles. The pinned SIP style isdesigned for through-hole application and has 10 pins spaced at 0.1" intervals.Pin 1 is on the far left of the board when viewed from the front. The package maybe inserted at right angles or bent to lie down (with the cover facing up) on thePCB. Avoid repeated bending of the pins as they may weaken and break. The surface-mount version is housed in a 24 pad hybrid SMD package whichhas been designed to facilitate both hand and automated assembly. Pin one ison the lower left when viewed as shown above. Castellation grooves have beenprovided for ease of hand soldering and inspection. PHYSICAL PACKAGINGRECOMMENDED PAD LAYOUTThe following drawings illustrate the recommended circuit-board footprints forthe HP-3 series transmitter modules. Be sure to also review the physical layoutand the antenna recommendations contained elsewhere in this guide.0.628"0.070"0.100"0.060".060".3".10".060".030" Dia. FinishedFigure 11: Suggested PCB FootprintSurface-Mount TransmitterPinned TransmitterFigure 10: Transmitter Physical PackageENCAPSULATION NOTICEIn some applications the designer may wish to encapsulate the product's circuitboard. Among the common reasons for doing so are environmental protectionand security. The dielectric constant of encapsulation and potting materialsvaries and can adversely affect transmitter performance. For this reason, Linxdoes not recommend the encapsulation of our products. Doing so will void allproduct warranties. It should be noted, however, that customers have reportedsuccess with a variety of encapsulation materials and techniques. Should youchoose to encapsulate your product, careful testing should be conducted todetermine the suitability of the chosen material.0.178"1.290"0.680"LOT 100001HP SERIES RF TRANSMITTERTXM-900-HP3-PP*0.125"0.628"1.260"LOT 100001HP SERIES RF TRANSMITTERTXM-900-HP3-SP*
Page 6PRODUCTION GUIDELINESPinned Transmitter Hand AssemblyThe SIP module pins may be hand or wave-soldered. The module should not besubjected to reflow. Linx recommends wash-free manufacturing techniques. Themodules are wash-resistant, but are not hermetically sealed. If a wash is used,a drying time, sufficient to allow the evaporation of any moisture which may havemigrated into the module, must be allowed prior to applying electrical power. Ifthe wash contains contaminants, transmitter performance may be adverselyaffected even after drying.SMD Transmitter Hand AssemblyThe SMD version is housed in a hybridSMD package which has been designedto support hand or automated reflowtechniques. The package’s primarymounting surface is the pads located onthe bottom of the module. Since thesepads are inaccessible during mounting,plated castellations run up the sides of themodule to facilitate solder wicking. Thisallows for very quick and efficient handsoldering for prototyping and smallvolume production.If the recommended pad placement has been followed, the pad on the board willextend slightly past the edge of the module. Touch both the PCB pad and themodule castellation with a fine soldering tip. Tack one module corner first, thenwork around the remaining attachment points being careful not to exceed thesolder times listed below.Care should be taken, especially when hand-soldering, not to use excessiveamounts of flux as it will wick under the module and potentially impair its function.In many cases, no-clean solder is the best choice. The modules are wash-resistant, but are not hermetically sealed. Linx recommends wash-freemanufacturing techniques. If a wash is used, a drying time, sufficient to allow anymoisture which may have migrated into the module to evaporate, must beallowed prior to applying electrical power. If the wash contains contaminants,transmitter performance may be adversely affected even after drying.CastellationsPCB PadsSoldering IronTipSolderFigure 12: Soldering TechniqueAbsolute Maximum Solder TimesHand-Solder Temp. TX +225°C for 10 Sec.Hand-Solder Temp. RX +225°C for 10 Sec.Recommended Solder Melting Point +180°CReflow Oven: +220° Max. (See adjoining diagram)
Page 7SMD TRANSMITTER AUTOMATED ASSEMBLY GUIDELINESFor high-volume assembly, most users will want to auto-place the modules. SMDversions of the modules have been designed to maintain compatibility with mostpick-and-place equipment, however, due to the module's hybrid nature certainaspects of the automated assembly process are far more critical than for othercomponent types. Following are brief discussions of the three primary areas where caution must beobserved.Reflow Temperature ProfileThe single most critical stage in the automated assembly process is the reflowprocess. The reflow profile below should not be exceeded since excessivetemperatures or transport times during reflow will irreparably damage themodules. Assembly personnel will need to pay careful attention to the oven'sprofile to ensure that it meets the requirements necessary to successfully reflowall components while remaining within the limits mandated by the modulesthemselves. Shock During Reflow TransportSince some internal module components may reflow along with the componentsplaced on the board being assembled, it is imperative that the module not besubjected to shock or vibration during the time solder is liquidus. WashabilityThe modules are wash-resistant, but are not hermetically sealed. Linxrecommends wash-free manufacturing techniques, however, the modules canbe subjected to a wash cycle provided that a drying time is allowed prior toapplying electrical power to the parts. The drying time should be sufficient toallow any moisture which may have migrated into the module to evaporate, thuseliminating the potential for shorting damage during power-up or testing. If thewash cycle contains contaminants, transmitter performance may be adverselyaffected, even after drying.Figure 13: Maximum Reflow Profile125°C600050100150200250300°C120 180 240 30030 90 150 210 270 330 360180°C210°C220°CTemperatureTime (Seconds)Ideal CurveLimit CurveForced Air Reflow Profile1-1.5 Minutes2-2.3 MinutesRamp-up Preheat ZoneCoolingSoak ZoneReflow Zone20-40 Sec.2 Minutes Max.
Page 8AmplifierVCO RF OutBand PassFilter28kHz Low PassFilterDataInPLL4MHzInt. Osc.MODECS0CS1CS212MHzCrystalModulatorFigure 14: HP-3 Series Transmitter Block Diagram THEORY OF OPERATIONThe TXM-HP3 is a high-performance, multi-channel RF transmitter capable oftransmitting both analog (FM) and digital (FSK) information. FM/FSK modulationoffers significant advantages over AM or OOK modulation methods includingincreased noise immunity and the receiver's ability to "capture" in the presence ofmultiple signals. This is especially helpful in crowded bands like those in which theHP-3 operates.Let's take a brief look at each transmitter section. A precision 12.00MHz Voltage-Controlled Crystal Oscillator (VCXO) serves as the frequency reference for thetransmitter. Incoming signals are filtered to limit their bandwidth and then used todirectly modulate this reference. Direct reference modulation inside the loopbandwidth allows a fast startup while allowing a wide modulation bandwidth andnear DC modulation capability. This results in accurate reproduction of analogand digital content and eliminates the need for code balancing.The modulated 12.00MHz reference frequency is applied to the Phase-LockedLoop (PLL). The PLL, combined with a 902-928MHz VCO, forms a stablefrequency synthesizer that can be programmed to oscillate at the desiredtransmit frequency. An on-board micro-controller manages the PLL programmingfunctions and greatly simplifies user interface. The micro-controller reads thechannel-selection lines and programs the on-board synthesizer. This frees thedesigner from complex programming requirements and allows for manual orsoftware channel selection. The micro-controller also monitors the status of thePLL and indicates when the transmitter is stable and ready to transmit data byraising the CTS line high.The PLL locked carrier is amplified and buffered to isolate the VCO from theantenna and to increase the output power of the transmitter. The output of thebuffer amplifier is connected to a filter network which suppresses harmonicemissions. Finally, the signal reaches the single-ended antenna port, which ismatched to 50 ohms to support commonly available antennas, such as thosemanufactured by Linx.
BOARD LAYOUT GUIDELINESIf you are familiar with RF you may be concerned about specialized layoutrequirements. Fortunately, by carefully adhering to a few basic design andlayout rules transmitter integration is generally very straightforward. Page 5 shows the suggested PCB footprintfor the HP-3 transmitter. A groundplane (aslarge as possible) should be placed on alower layer of your PC board opposite thetransmitter. This groundplane can also becritical to the performance of your antennawhich will be discussed later in themanual. The transmitter should be kept away from other components on your PCB,especially high-frequency noise sources such as an oscillator or switching supply.To mount a pinned version of the transmitter parallel to the PC board, bend itover so that the plastic cover faces away from the board. Do not route PCB traces directly under SMD packaged versions. The undersideof the module has numerous signal-bearing traces and vias which could short orcouple to traces on the product's circuit board.The trace from the transmitter to the antenna should be kept as short aspossible. For runs greater than 1/4 inch use 50-ohm coax or a 50-ohm microstriptransmission line as shown below. Handy software for calculating microstriplines is available on the Linx website (www.linxtechnologies.com).The typical output power of the HP-3 transmitter isright at Part-15 limits. Sometimes, it is necessaryto slightly attenuate the output to compensate forantenna gain. This is accomplished using a three-resistor attenuation network as shown. While thisnetwork is often referred to as a “T” pad the actualresistor orientation is usually not critical. Use onlysurface-mount type resistors grouped closely. Theseries pads may be bridged if the network is not needed. Further details can befound in application note #00150 - "Use and Design of T-Attenuation Pads".Page 9Full groundplane on inner or lower board layerMicrostripFigure 15: Groundplane TreatmentFigure 16: Microstrip Formulas (Er = Dielectric constant of pc board material)TYPICAL LAYOUTMICROSTRIPSGROUNDRF INANT.R1R1R2GROUNDPLANEON LOWER LAYERFigure 17: T-pad LayoutEffectiveDielectric Width/Height Dielectric CharacteristicConstant (W/d) Constant Impedance4.8 1.8 3.59 50.0423.07 51.02.55 3 2.12 48.0
POWER SUPPLY GUIDELINESThe user must provide a clean source ofpower to the transmitter to ensure properoperation. The HP-3 incorporates a precisionlow-dropout regulator on-board which allowsoperation over an input voltage range of 2.8 to13 VDC. Figure 18 shows a typical supplyfilter. This filter should be placed close to themodule's supply lines. Its actual values willdepend on the type and frequency of noisepresent in the user's product.The HP-3 can be put into an ultra-low-current (<15µA) power-down mode byholding the PDN pin low. If the PDN pin is left open or held high, the transmitterwill turn on. In power-down mode, the transmitter is completely shut down.Page 10POWER-UP SEQUENCEThe HP-3 transmitter is controlledby an on-board microprocessor.When power is applied, a start-upsequence is executed. At the end of the start-up sequence, thetransmitter is ready to transmit data.Figure 19 shows the start-upsequence. This sequence isexecuted when power is applied tothe VCC pin or when the PDN pin iscycled from low to high. On power-up, the on-board micro-processor reads the externalchannel-selection lines (parallelmode) or serial channel input (serialmode) and sets the frequencysynthesizer to the appropriatechannel. Figure 3 on page 3 showsthe typical turn-on response time foran HP-3 transmitter. When thefrequency synthesizer has lockedon to the proper channel frequency, the circuit is ready to accept data. This isacknowledged by the CTS line transitioning high. The module will then transmitanalog or digital data from the user's circuit.The module can be put into an ultra-low-current (<15µA) power-down mode byholding the PDN pin low. This removes all power from the transmitter's circuitry.If PDN is left floating or held high, the transmitter will wake up and begin normaloperation. No transmitter functions work when PDN is low. POWER ONDetermine ModeRead Channel-Selection InputsProgram Freq. SynthTo Default CH. 50Program FrequencySynthesizerCrystal OscillatorBegins to OperateCrystal OscillatorBegins to WorkReady forSerial Data InputProgram FrequencySynthesizerDetermine State ofCTS Output PinCycle Here Until MoreData Input, Mode Change or PLL Loses LockDetermine State ofCTS Output PinCycle Here Until Channel or Mode ChangeSerial ModeParallel ModeFigure 18: Typical Supply FilterFigure 19: Start-up Sequence.1µF>22µFVcc INVcc tomodule
Page 11CHANNEL SELECTIONParallel SelectionAll HP-3 transmitter models featureeight parallel selectable channels.Parallel mode is selected bygrounding the mode pin. In this mode,channel selection is determined bythe logic states of pins CS0-CS2 asshown in Figure 20. In this table a "0"represents ground and a "1" the positive supply. The on-board microprocessorperforms all PLL loading functions, eliminating external programming andallowing channel selection via DIP switches or a product's processor. Serial SelectionIn addition to the parallel mode, PS versions of the HP-3 also feature 100 seriallyselectable channels. The serial mode is entered when the mode pin is left openor held high. In this condition CS1 and CS2 become a synchronous serial portwith CS1 serving as the clock line and CS2 as the data line. The module is easilyprogrammed by sending and latching the binary number (0-100) of the desiredchannel (see page 22 for channel selection table). With no additional effort themodule's on-board microprocessor handles the complex PLL loading functions. The serial mode isstraightforward, however,minimum timings and bitorder must be followed.Loading is initiated bytaking the clock line highand the data line low asshown. The eight-bitchannel number is thenclocked in one bit at a timewith the LSB first. Figure 20: Parallel Channel Select TableVariable DataNote 3Note 2Note 112345678T125µsT2 5µs T38µsT45µsDataClock T01ms(T0) Minimum time between packets or prior to data startup...................................1mS min.(T1) Data-LO/Clock-HI to Data-LO/Clock-LO..............................................................25µS min.(T2) Clock-LO to Clock-HI..............................................................................................5µS min.(T3) Clock-HI to Clock-LO..............................................................................................8µS min.(T4) Data-HI/Clock-HI......................................................................................................5µS min.Total Packet Time ..........................................................................................................157µS min.1) Loading begins when clock line is high and data line is taken low. 2) Ensure that the edge is fully risen prior to the high-clock transition.3) Both lines high - triggers automatic latchFigure 21: PLL Serial Programming Timing TableThere is no maximum time for this process, only the minimum times which must beobserved. After the eighth bit both the clock and data lines should be taken high totrigger the automatic data latch. A typical software routine can complete the loadingsequence in under 200µS. A sample routine is available on the Linx website.NOTE: When the module is powered up in the serial mode it will default to channel 50 untilprogrammed by user software. This allows testing apart from external programming andprevents out-of-band operation. When programmed properly, the dwell time on this defaultchannel can be less than 200µS. Channel 50 is not counted as a usable channel sincetransmitters defaulting to the channel might interfere with a transmitter intentionallyoccupying the channel. If a loading error occurs, such as a channel number >100 or atiming problem, the receiver will default to serial channel 0. This is useful for debugging asit verifies serial port activity.CS2 CS1 CS0 Channel Frequency000 0 903.37001 1 906.37010 2 907.87011 3 909.37100 4 912.37101 5 915.37110 6 919.87111 7 921.37
Page 12INPUTTING ANALOG SIGNALSThe HP-3 series transmitter is capable of sending a wide range of analog signalsincluding audio. The ability of the HP-3 to send combinations of audio and dataalso opens new areas of opportunity for creative design. Simple or complex analog signals within the specified analog bandwidth andinput levels may be connected directly to the transmitter’s DATA pin. Thetransmitter input is high impedance (200k) and can be directly driven by a widevariety of sources ranging from a single frequency to complex content such asvoice or music. Analog signals at the data input pin may range from 50 Hz to28kHz. The Typical Performance Graphs on page 3 of this manual illustrate themodulation linearity for a variety of simple waveforms. The HP3 is a single supply deviceand as such is not capable ofoperating in the negative voltagerange, therefore analog sourcesshould typically provide a 0V to3V, but not more than 5V P-P,maximum waveform and should,in most cases, be AC-coupled intothe DATA pin to achieve the bestperformance. The size of thecoupling capacitor should be largeenough to ensure the passage ofall desired frequencies and, at thesame time, small enough to allowthe start-up time desired. After the AC signal passes into the modulation circuitit will be automatically adjusted to the optimum DC offset by an internal voltagedivider. Since the modulation voltage applied to the DATA pin determines thecarrier deviation, distortion can occur if the DATA pin is over-driven. The actuallevel of the input waveform should be adjusted to achieve optimum in-circuitresults for your application.The illustration above shows the simplicity of transmitting audio with the HP-3transmitter. In applications where higher audio quality is required, an externalcompandor such as a Phillips SA576, may be employed to increase dynamicrange and reduce noise. The HP-3 is capable of providing audio qualitycomparable to a radio or intercom. When true high-fidelity audio is required, theHP will probably not be the best choice, as it has been optimized for data. Adevice designed specifically for high quality audio should be utilized instead.GNDANTCHS 0CHS 1 SS CLOCKCHS 2 SS DATACTSPOWER DOWNVCCGND/MODEDATA INVCCChannelSelectTX1S13-PositionDIP SwitchAudio In FromHeadphone Or Speaker JackOf Amplifier/Tape Player, etc.Figure 22: Typical Voice TransmitterCTS OUTPUTThe Clear-To-Send (CTS) output goes high to indicate the transmitter PLL islocked and the module is ready to accept data. In a typical application, a micro-controller will raise the PDN line high (powering-up the transmitter) and begin tomonitor the CTS line. When the line goes high, the micro-controller would startsending data. It is not necessary to use the CTS output. In applications whereCTS is not used, the user's circuit should wait a minimum of 10mSec after raisingthe PDN pin high before transmitting data. If data is being sent redundantly, thereis generally no need to monitor the CTS pin or to wait a fixed time.
Page 13INPUTTING DIGITAL DATAThe data input pin may be directly connected to virtually any digital peripheralincluding microcontrollers, encoders, and UART’s. The data input has animpedance of 200kΩ and can be used with any data that transitions from 0V toa 3V-5V peak amplitude within the specified bandwidth of the module. While it ispossible to send data at rates higher than specified, the internal data filter willcause severe roll off and attenuation. Many RF products require a fixed data transition rate or place tight constraintson the mark/space ratio of the data being sent. Thankfully, the HP-3 transmitterarchitecture eliminates such considerations and allows virtually any signal,including PWM, Manchester and NRZ data to be sent at rates from 100bps to56kbps. This is accomplished by directly modulating the PLL’s frequencyreference within the loop filter bandwidth. By doing so, the loop filter can beoptimized for rapid startup while allowing near DC modulation.Unlike a radio modem the HP-3 does not encode or packetize the data in anymanner. This transparency gives the designer great freedom in software andprotocol development. A designer may also find creative ways to utilize the abilityof the transmitter to accept both digital and analog signals. For example, anapplication might transmit voice in analog then send out a digital controlcommand. Such mixed mode systems, which combine analog signals and datacan greatly enhance the function and versatility of many products without asignificant increase in implementation cost. It is always important to think of an RF link as a total system taking into accountboth the transmitter and receiver characteristics. The incoming data must notonly be compatible with the transmitter but also within the capability of thereceiver to reproduce it. For example, if the transmitter were sending a 255 (0FFhex) continuously the receiver would view the stream of high bits as a DC level.The receiver would hold that level until a transition was required to meet itsminimum transition frequency requirement. If no transition occurred, dataintegrity could not be guaranteed. The HP-3 transmitter has been designed forcompatibility with all generations of HP receivers. While it can potentially be usedwith receivers from other manufacturers we do not recommend it. The easiestapplication and field reliability will be obtained when HP family components areused for the entire link. PROXIMITY OPERATIONMultiple transmitters may be active on separate channels so long as an adjacentchannel's signal does not enter the receiver at a level exceeding the rejectioncapability of the receiver. In serial mode the channels are closely spaced and willnot all be useable in proximity. The large number of channels is not meant to implythat all can be successfully used in close proximity. The high channel count isprovided to accommodate hopping, allow compatibility with a broad range ofreceiver frequencies, and allow agility in avoiding other interference sources. Incases where the modules are combined to form a transceiver they should beoperated in half-duplex, meaning that only the transmitter or receiver is active atany time. Full-duplex operation is possible but will result in reduced range due toreceiver desensing from the closely adjacent transmitter..
Page 14DATA CONSIDERATIONSOnce an RF link has been established, the challenge becomes how to effectivelytransfer information across it. For simple control or status signals, such as buttonpresses or switch closures, consider using an encoder and decoder IC set.These chips are available from several manufacturers including Linx, Microchip,Holtek, and Motorola. These chips take care of all encoding, error checking, anddecoding functions. They generally provide a number of inputs to which switchescan be directly connected, and address or security bits to prevent unintentionalactivation. These IC's are an excellent way to avoid protocol development andbring basic remote control/status products quickly and inexpensively to market. In most applications the modules will be interfaced to a microprocessor. A UARTmay be employed or an output pin of the microprocessor "bit-banged" to createa data stream. While many RF solutions impose complex formatting andbalancing requirements, the HP-3 series was designed to be as transparent aspossible. The HP-3 does not encode or packetize the data in any manner. Thistransparency gives the designer tremendous flexibility in the structure of aprotocol. Of course the performance and reliability of the link are dependent onthe quality of external software and hardware. To properly apply the transmitter,it is critical to understand the differences between a wired and a wirelessenvironment. At each point in the system there are timing and data-corruptionissues that should be understood and accounted for. The following sectionprovides a brief overview of these issues. You may also wish to read Applicationnote 161 (Considerations for Sending Data Using the HP-3 Series) prior tobeginning code development. GNDANTCHS 0CHS 1 SS CLOCKCHS 2 SS DATACTSPOWER DOWNVCCGND/MODEDATA INVCC VCCVCCChannelSelectTX1S13-PositionDIP SwitchR12.2K316++++C14.7 uFC24.7 uFC34.7 uF1213456158J1DB-9FSerialConnector5C44.7 uFU1Max 23221314Figure 24: Typical Application: RS-232 InterfaceGNDANTCHS 0CHS 1 SS CLOCKCHS 2 SS DATACTSPOWER DOWNVCCGND/MODEDATA IND0D1D2D3DOUTTEOSC1OSC2GNDVCCA7A6A5A4A3A2A1A0VCCChannelSelectTX1S13-PositionDIP SwitchR1390KS3S4D1IN914D2S28-PositionDIP SwitchAddress SelectHoltekHT680Figure 23: Typical Application: Remote-Control Transmitter
Page 15PROTOCOL CONSIDERATIONSAs previously indicated, the module's transparency allows for virtually unlimitedprotocol types and techniques.This section is meant only to illustrate generalissues a designer should address to ensure product reliability in the field. Yourapplication may call for or benefit from an entirely different protocol structure.It is a good idea to structure the data being sent into small packets so that errorscan be managed without affecting large amounts of data. Packets should betransmitted without space between bytes. When using a UART the followingpacket format is often followed:[ uart sync byte ] [ start byte ] [ data packet ]The UART sync-byte is used to ensure that the start-bit for the start-byte will becorrectly detected. It is a single byte with a value of 255 (0FF hex). A start-byteoften follows the sync-byte to intelligently qualify the data-packet which willfollow. Detection of the start-byte would be performed by the computer ormicrocontroller connected to the receiver.TIMING CONSIDERATIONSTiming plays a key role in link reliability especially when the modules are beingrapidly turned on and off or hopping channels. Unlike a wire, allowance must bemade for the programming and settling times of both the transmitter and receiverotherwise portions of the signal being sent will be lost. There are two majortiming considerations the engineer must be aware of when designing with theHP-3 Series transmitter. These are shown in the table below. Remember thestated timing parameters assume a stable supply of 2.8 volts or greater. They donot include the charging times of external capacitance on the module's supplylines, the overhead of external software execution, or power supply rise times. Parameter Description Max.T1Transmitter Turn-on Time 10mSecT2Max Channel-Change Time 1.5mSec(Time to Valid Data)T1is the maximum time required for the transmitter to power-up and lock on-channel. This time is measured from the application of VCC to the CTS outputtransitioning high. T2is the worst-case time needed for a powered-up module to switch betweenchannels from a valid channel selection. This time does not include externaloverhead for loading a desired channel in the serial channel-selection mode.Normally, the transmitter will be turned off after each transmission. This iscourteous use of the airwaves and reduces power consumption. The transmittermay be shutdown by switching its supply or the PDN pin. In power-down themodule is completely shut down. When the transmitter is again powered upallowance must be made for the requirements above. In many cases the transmitter will lock more quickly than the times indicated. Ininstances where turn-around time or power consumption are critical the CTS pinshould be monitored so data can be sent immediately upon transmitterreadiness.
Page 16PROTOCOL CONSIDERATIONS (CONT.)The procedure here is protocol-dependent, but to illustrate let's consider thepacket format outlined on the preceding page being sent to a UART. A UARTinterprets the start-bit of a byte as a 1-0 transition. When the incoming data is101010, or hash, it is hard actually to find the start bit. This problem is solved bythe UART sync-byte. The purpose of the sync-byte is to create a high markingperiod of at least a byte-length so that the start bit of the following start-byte canbe correctly recognized. The start-byte is used by the receiving computer or microcontroller to intelligentlyidentify the beginning of a data packet. The start-byte value should be chosen sothat it does not appear in the data stream. Otherwise, a microntroller may "wakeup" in the middle of a packet and interpret data in the packet as a valid start-byte.There are many other ways to organize protocol if this proves impractical.There is always a possibility of bursting errors from interference or changingsignal conditions causing corruption of the data packet, so some form of errorchecking should be employed. A simple checksum or CRC could be used. Oncean error is detected the protocol designer may wish to simply discard the corruptdata or develop a scheme for correcting it or requesting its retransmission.INTERFERENCE CONSIDERATIONSIt must be recognized that many bands, such as those in which the HP-3operates, are widely used, and the potential for conflict with other unwantedsources of RF is very real. All RF products are at risk from interference but itseffects can be minimized by better understanding its characteristics.Interference can manifest itself in many ways. Low-level interference willproduce noise and hashing on the output and reduce the link's overall range.Thanks to the capture properties of an FM system, the receiver will still functionwhen an intended signal is present at a higher level than the interference.Another type of interference can be caused by higher-powered devices such ashopping spread-spectrum devices. Since these devices move rapidly fromfrequency to frequency they will usually cause short, intense losses ofinformation. Such errors are referred to as bursting errors and will generally bedealt with through protocol.High-level interference is caused by products sharing the same frequency orfrom near-band high-power devices. Fortunately, this type of interference is lesscommon than those mentioned previously, but in severe cases can prevent alluseful function of the affected device. It is in these cases that the frequencyagility offered by the HP-3 is especially useful. Although technically it is not interference, multipath is also a factor to beunderstood. Multipath is a term used to refer to the signal cancellation effectsthat occur when RF waves arrive at the receiver in different phase relationships.This is particularly a factor in interior environments where objects provide manydifferent reflection paths. Multipath results in lowered transmitter signal levels atthe receiver and thus shorter useful distances for the link.The receiver's Received Signal Strength Indicator (RSSI) output can be used toqualify the presence and strength of interference and identify the best channelsfor use in a given environment. Refer to the HP-3 receiver guide for more details.
Page 17GENERAL ANTENNA RULESThe following general rules should help in maximizing antenna performance:1. Proximity to objects such as a user's hand or body, or metal objects will causean antenna to detune. For this reason the antenna shaft and tip should bepositioned as far away from such objects as possible.2. Optimum performance will be obtained from a 1/4- or 1/2-wave straight whipmounted at a right angle to the groundplane. In many cases, this isn't desirablefor practical or ergonomic reasons; thus, an alternative antenna style such asa helical, loop, patch, or base-loaded whip may be utilized and thecorresponding sacrifice in performance accepted.3. If an internal antenna is used, keep it away from other metal components,particularly large items like transformers, batteries, and PCB tracks andgroundplanes. In many cases, the space around the antenna is as importantas the antenna itself. 4. In many antenna designs, particularly 1/4-wave whips,the groundplane acts as a counterpoise, forming, inessence, a 1/2-wave dipole. For this reason adequategroundplane area is essential. The groundplane can be ametal case or ground-fill on the circuit board. Ideally, thegroundplane to be used as counterpoise should have asurface area ≥ the overall length of the 1/4-waveradiating element and be oriented at a 90° angle. Suchan orientation is often not practical due to size andconfiguration constraints. In theseinstances a designer must make thebest use of the area available to createas much groundplane in proximity to thebase of the antenna as possible. Ininstances where the antenna isremotely located or the antenna is not inclose proximity to a circuit board planeor grounded metal case, a small metalplate may be fabricated to maximizeantenna performance.5. Remove the antenna as far as possiblefrom potential interference sources such as switching power supplies,oscillators, motors and relays. Remember, the single best weapon againstsuch problems is attention to placement and layout. Filter the module's powersupply with a high-frequency bypass capacitor. Place adequate groundplaneunder all potential sources of noise. Shield noisy board areas wheneverpractical.6. In some applications it is advantageous to place the receiver and its antennaaway from the main equipment. This avoids interference problems and allowsthe antenna to be oriented for optimum RF performance. Always use 50Ωcoax, such as RG-174, for the remote feed.IEDIPOLEELEMENTGROUNDPLANEVIRTUAL λ/4DIPOLE λ/4 λ/4 VERTICAL λ/4 GROUNDEDANTENNA (MARCONI)OPTIMUMUSEABLE NOT RECOMMENDEDNUT GROUNDPLANE (MAY BE NEEDED)CASEFigure 25: Antenna Orientations
ANTENNA CONSIDERATIONSThe choice of antennas is one of themost critical and often overlookeddesign considerations. The range,performance, and legality of thetransmitter is critically dependent onthe antenna utilized. While adequateantenna performance can often beobtained by trial and error methods,professionally designed antennas,such as those offered by Linx, canprovide superior performance,repeatability and legal compliance.For complete details on the Linx antenna line, visit the Linx website atwww.linxtechnologies.com, or call (800)736-6677The following sections look at some of the basic considerations involved in the design andselection of antennas. For a more comprehensive discussion please refer to Linxapplications note #00500 "Antennas: Design, Application, Performance". Page 18CONNECTOR OPTIONSThe FCC requires that antennasdesigned for use on Part 15products be either permanentlyattached, or utilize a unique andproprietary connector not availableto the general public. In caseswhere the antenna needs to beremovable, Linx offers a full line ofconnectors designed to comply withthese requirements. Figure 26: Linx AntennasFigure 27: Linx Connectors ANTENNA SHARINGIn cases where a transmitter and receivermodule are combined to form a transceiverit is often advantageous to share a singleantenna. To accomplish this an antennaswitch must be used to provide isolationbetween the modules. There is a widevariety of antenna switches availablewhich are cost-effective and straight-forward to use. Among the most popularare switches from Alpha and NEC. Lookfor an antenna switch that has highisolation and low loss at the desiredfrequency of operation. Generally, the TX or RX status of a switch will becontrolled by a product's microprocessor, but selection may also be mademanually by the user. In some cases where the characteristics of the TX and RXantennas need to be different or switch losses are unacceptable it may be moreappropriate to utilize two discrete antennas. AntennaTransmitterModuleReceiverModule0.1µF0.1µF0.1µF0.1µF0.1µFGNDGNDVDDSelectFigure 28: Typical Antenna Switch
Page 19Specialty StylesWhip StyleLoop Style1/4-wave wire lengthfrequencies:433MHz = 6.5"868MHz = 3.24"902-928MHz = 3.06"Awhip-style monopole antenna provides outstanding overallperformance and stability. A low-cost whip can be easily fabricated fromwire or rod, but most product designers opt for the consistentperformance and cosmetic appeal of a professionally made model. Tomeet this need, Linx offers a wide variety of straight and reduced-heightwhip-style antennas in permanent and connectorized mounting styles. The wavelength of the operational frequency determines an antenna'soverall length. Since a full wavelength is often quite long, a partial 1/4-wave antenna is normally employed. Its size and natural radiationresistance make it well-matched to Linx modules. The approximatelength for a straight 1/4-wave antenna can be easily found using theformula below. It is also possible to reduce the overall height of theantenna by using a helical winding; therefore, the physical appearanceis not always an indicator of the antenna's frequency.Linx offers a wide variety of specialized antenna styles and variations.Many of these styles utilize helical elements to reduce the overallantenna size while maintaining excellent performance characteristics. Ahelical antenna's bandwidth is often quite narrow and the antenna candetune in proximity to other objects, so care must be exercised in layoutand placement. Aloop- or trace-style antenna is normally printed directly on a product'sPCB. This makes it the most cost-effective of antenna styles. Theelement can be made self-resonant or externally resonated withdiscrete components but its actual layout is usually product-specific.Despite its cost advantages, PCB antenna styles are generallyinefficient and useful only for short-range applications. Loop-styleantennas are also very sensitive to changes in layout or substratedielectric which can introduce consistency issues into the productionprocess. In addition, printed styles initially are difficult to engineer,requiring the use of expensive equipment including a network analyzer.An improperly designed loop will have a high SWR at the desiredfrequency which can introduce instability in the RF stages.Linx offers low-cost planar and chip antennas which mount directly to aproduct's PCB. These tiny antennas do not require testing and provideexcellent performance in light of their compact size. They are anexcellent alternative to the often problematic "printed" antenna.L =234FMHz234 = .255.255 x 12" = 3.06"916MHzWhere:L=length in feet of quarter-wavelength F=operating frequency in megahertzCOMMON ANTENNA STYLESThe antenna is a critical and often overlooked component which has a significanteffect on the overall range, performance and legality of an RF link. There arehundreds of antenna styles that can be employed with the HP-3 Series. Followingis a brief discussion of styles commonly utilized in compact RF designs.
Page 20LEGAL CONSIDERATIONSWhen working with RF, a clear distinction must be made between what is technicallypossible and what is legally acceptable in the country where operation is intended.Many manufacturers have avoided incorporating RF into their products as a result ofuncertainty and even fear of the approval and certification process. Here at Linx ourdesire is not only to expedite the design process, but also to assist you in achievinga clear idea of what is involved in obtaining the necessary approvals to legally marketyour completed product. In the United States the approval process is actually quite straightforward. Theregulations governing RF devices and the enforcement of them are the responsibilityof the Federal Communications Commission (FCC). The regulations are contained inthe Code of Federal Regulations (CFR), Title 47. Title 47 is made up of numerousvolumes; however, all regulations applicable to this module are contained in volume0-19. It is strongly recommended that a copy be obtained from the GovernmentPrinting Office in Washington, or from your local government book store. Excerpts ofapplicable sections are included with Linx evaluation kits or may be obtained from theLinx Technologies web site (www.linxtechnologies.com). In brief, these rules requirethat any device which intentionally radiates RF energy be approved, that is, tested,for compliance and issued a unique identification number. This is a relatively painlessprocess. Linx offers full EMC pre-compliance testing in our HP/Emco-equipped testcenter. Final compliance testing is then performed by one of the many independenttesting laboratories across the country. Many labs can also provide other certificationsthe product may require at the same time, such as UL, CLASS A/B, etc. Once yourcompleted product has passed, you will be issued an ID number which is then clearlyplaced on each product manufactured. Questions regarding interpretations of the Part 2 and Part-15 rules or measurementprocedures used to test intentional radiators, such as the HP-3 modules, forcompliance with the Part-15 technical standards, should be addressed to:Federal Communications Commission Equipment Authorization Division Customer Service Branch, MS 1300F2 7435 Oakland Mills Road Columbia, MD 21046 Tel: (301) 725-1585 / Fax: (301) 344-2050 E-Mail: labinfo@fcc.govInternational approvals are slightly more complex, although many modules aredesigned to allow all international standards to be met. If you are considering theexport of your product abroad, you should contact Linx Technologies to determine thespecific suitability of the module to your application.All Linx modules are designed with the approval process in mind and thus much ofthe frustration that is typically experienced with a discrete design is eliminated.Approval is still dependent on factors such as the choice of antennas, correct use ofthe frequency selected, and physical layout. While some extra cost and design effortare required to address these issues, the additional usefulness and profitability addedto a product by RF makes the effort more than worthwhile.NOTE: HP-3 Series modules are intended to allow for full Part-15 compliance;however, they are not approved by the FCC or any other agency worldwide. Thisis because the module's performance and legality may be affected by externalfactors specific to a user's application. The purchaser understands that testingand approvals of a finished product may be required prior to the sale or operationof the device, and agrees to utilize the component in keeping with all lawsgoverning their use in the country of operation.
Page 2100100 RF 101: Information for the RF challenged00126 Considerations for operation in the 902Mhz to 928Mhz band00130 Modulation techniques for low-cost RF data links00140 The FCC Road: Part 15 from concept to approval00150 Use and design of T-attenuation pads00155 Serial loading techniques for the HP-3 Series (PS Versions)00161 Considerations for sending data with the HP-3 Series 00500 Antennas: Design, Application, PerformanceNOTE # LINX APPLICATION NOTE TITLESURVIVING AN RF IMPLEMENTATIONThe addition of wireless capabilities brings an excitingnew dimension to any product. It also means thatadditional effort and commitment will be needed to bringthe product successfully to market. By utilizing an RFmodule, such as the HP-3, the design and approvalprocess will be greatly simplified. It is still important,however, to have an objective view of the stepsnecessary to ensure a successful RF integration. Sincethe capabilities of each customer vary widely it is difficultto recommend one particular design path, but mostprojects follow steps similar to those shown at the right.In reviewing this sample design path you may noticethat Linx offers a variety of services, such asantenna design, and FCC prequalification, that areunusual for a high-volume component manufacturer.These services, along with an exceptional level oftechnical support, are offered because we recognizethat RF is a complex science requiring the highestcaliber of products and support. "Wireless MadeSimple" is more than just a motto, it's ourcommitment. By choosing Linx as your RF partnerand taking advantage of the resources we offer, youwill not only survive implementing RF, but you mayeven find the process enjoyable.HELPFUL APPLICATION NOTES FROM LINXIt is not the intention of this manual to address in depth many of the issues thatshould be considered to ensure that the modules function correctly and deliverthe maximum possible performance. As you proceed with your design you maywish to obtain one or more of the following application notes, which address indepth key areas of RF design and application of Linx products. Theseapplications notes are available on-line at www.linxtechnologies.com or bycontacting the Linx literature department.DECISION TO UTILIZE RF IS MADERESEARCH RF OPTIONSLINX MODULE IS CHOSENORDER EVALUATION KIT(S)TEST MODULE(S) WITHBASIC HOOKUPINTERFACE TO CHOSEN CIRCUIT AND DEBUGCONSULT LINX REGARDINGANTENNA OPTIONS AND DESIGNLAY OUT BOARDSEND PRODUCTION-READYPROTOTYPE TO LINXFOR EMC PRESCREENINGOPTIMIZE USING RF SUMMARY GENERATED BY LINXSEND TO PART 15TEST FACILITYRECEIVE FCC ID #COMMENCE SELLING PRODUCTTYPICAL STEPS FORIMPLEMENTING RF
Page 22SERIAL CHANNEL SELECTION TABLECHANNEL TX FREQUENCY RX LO CHANNEL TX FREQUENCY RX LO0 902.62 867.92 51 915.37 880.671 902.87 868.17 52 915.62 880.922 903.12 868.42 53 915.87 881.173 903.37 868.67 54 916.12 881.424 903.62 868.92 55 916.37 881.675 903.87 869.17 56 916.62 881.926 904.12 869.42 57 916.87 882.177 904.37 869.67 58 917.12 882.428 904.62 869.92 59 917.37 882.679 904.87 870.17 60 917.62 882.9210 905.12 870.42 61 917.87 883.1711 905.37 870.67 62 918.12 883.4212 905.62 870.92 63 918.37 883.6713 905.87 871.17 64 918.62 883.9214 906.12 871.42 65 918.87 884.1715 906.37 871.67 66 919.12 884.4216 906.62 871.92 67 919.37 884.6717 906.87 872.17 68 919.62 884.9218 907.12 872.42 69 919.87 885.1719 907.37 872.67 70 920.12 885.4220 907.62 872.92 71 920.37 885.6721 907.87 873.17 72 920.62 885.9222 908.12 873.42 73 920.87 886.1723 908.37 873.67 74 921.12 886.4224 908.62 873.92 75 921.37 886.6725 908.87 874.17 76 921.62 886.9226 909.12 874.42 77 921.87 887.1727 909.37 874.67 78 922.12 887.4228 909.62 874.92 79 922.37 887.6729 909.87 875.17 80 922.62 887.9230 910.12 875.42 81 922.87 888.1731 910.37 875.67 82 923.12 888.4232 910.62 875.92 83 923.37 888.6733 910.87 876.17 84 923.62 888.9234 911.12 876.42 85 923.87 889.1735 911.37 876.67 86 924.12 889.4236 911.62 876.92 87 924.37 889.6737 911.87 877.17 88 924.62 889.9238 912.12 877.42 89 924.87 890.1739 912.37 877.67 90 925.12 890.4240 912.62 877.92 91 925.37 890.6741 912.87 878.17 92 925.62 890.9242 913.12 878.42 93 925.87 891.1743 913.37 878.67 94 926.12 891.4244 913.62 878.92 95 926.37 891.6745 913.87 879.17 96 926.62 891.9246 914.12 879.42 97 926.87 892.1747 914.37 879.67 98 927.12 892.4248 914.62 879.92 99 927.37 892.6749 914.87 880.17 100 927.62 892.9250* 915.12 880.42*This channel is not counted as it is the Serial Mode default channel (see page 11)
Page 23VSWR Insertion Power PowerLoss Transmitted Reflected(dB) (%) (%)17.391 -6.87 20.57% 79.43%11.610 -5.35 29.21% 70.79%8.724 -4.33 36.90% 63.10%6.997 -3.59 43.77% 56.23%5.848 -3.02 49.88% 50.12%5.030 -2.57 55.33% 44.67%4.419 -2.20 60.19% 39.81%3.946 -1.90 64.52% 35.48%3.570 -1.65 68.38% 31.62%3.010 -1.26 74.88% 25.12%2.615 -0.97 80.05% 19.95%2.323 -0.75 84.15% 15.85%2.100 -0.58 87.41% 12.59%1.925 -0.46 90.00% 10.00%1.433 -0.14 96.84% 3.16%1.222 -0.04 99.00% 1.00%1.119 -0.01 99.68% 0.32%1.065 0.00 99.90% 0.10%1.034 0.00 99.97% 0.03%1.020 0.00 99.99% 0.01%MISMATCH CONVERSION TABLENOTES:
Page 24LINX TECHNOLOGIES, INC.575 S.E. ASHLEY PLACEGRANTS PASS, OR 97526Phone: (541) 471-6256FAX: (541) 471-6251http://www.linxtechnologies.comU.S. CORPORATE HEADQUARTERS:Linx Technologies is continually striving to improve the quality and function of its products; forthis reason, we reserve the right to make changes without notice. The information contained inthis Data Sheet is believed to be accurate as of the time of publication. Specifications are basedon representative lot samples. Values may vary from lot to lot and are not guaranteed. LinxTechnologies makes no guarantee, warranty, or representation regarding the suitability of anyproduct for use in a specific application. None of these devices is intended for use inapplications of a critical nature where the safety of life or property is at risk. The user assumesfull liability for the use of product in such applications. Under no conditions will Linx Technologiesbe responsible for losses arising from the use or failure of the device in any application, otherthan the repair, replacement, or refund limited to the original product purchase price. Somedevices described in this publication are patented. Under no circumstances shall any user beconveyed any license or right to the use or ownership of these patents.Disclaimer©2003 by Linx Technologies, Inc. The stylizedLinx logo, Linx, and "Wireless Made Simple"are the trademarks of Linx Technologies, Inc. Printed in U.S.A.

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