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G-7901D Telemeter FS Transmitter
G-7902C FSK Receiver
G-7903B&C Analog Multiplexers

The G-7901D and G-7902C telemetry system provides higher accuracy and greater temperature stability than conventional telemetering systems. These features stem from the extensive use of crystal stabilized oscillators for frequency synthesis and detection circuits. Typical telemeter converter accuracy is better than 0.1% over a temperature span of 0 to 50 degrees C. Plug-in filter sections are standard.

The G7902C Telemeter, FS Receiver linearly regenerates a dc voltage or current from subaudio frequency modulated FS tones.The on-board frequency shift(FS) receiver accepts frequency shift tones from a standard voice grade telecommunication channel in the range of 420 Hz and 10 kHz. The input filter of the FS receiver exhibits a 600 ohms rising impedance out of band. Attenuation at adjacent channels is greater than 40dB allowing the frequency multiplexing of several receivers onto one transmission medium. The FS receiver detects the subaudio frenquency which in turn is discriminated into an analog output by the phase-locked loop section. An integrating amplifier transforms the phase-locked loop feedback voltage to generate the calibrated output voltage.

The output of the telemeter converter section can have spans in the range of 100 mV to 10 V and current loops to 20 mA using an optional driver amplifier. The G-79902C can also be configured to realize subaudio frequencies other than the standard 10 to 30 Hz such as 5 to 15 Hz, 18 to 30 Hz and 5 to 25 Hz. An LED is provided on the front panel for visual indication of the presence of both the subaudio and carrier frequencies.

An operational amplifier buffer stage can be employed when the drive currents of the voltage output exceed 1 mA or when a current loop output is required. The current amplifier is capable of supplying up to 30 mA in either configuration.

Carrier detector alarm and modulation fail alarm curcuits are standard on the G-7902C. The presence of both the carrier frequency and the subaudio frequency can operate two relays to indicate transmission status. Upon loss of either or both the carrier and subaudio frequencies, the relays will deenergize in 0.2 second to indicate an alarm. Upon restoration of both frequencies, an adjustable delay current from 1 to 10 seconds will occur before the relays reenergize to indicate a return from alarm.

A dc-dc converter can be added to the G-7902C to completely isolate the output stage. This allows the user to drive current loops with a ground without regard to the placement of the tone equipment's ground.
Specifications

CRYSTAL OSCILLATOR CONTROLLED WIDE TEMPERATURE OPERATION ACCURACY TO WITHIN 0.15% INDICATED CARRIER AND MODULATION FAIL OUTPUTS VOLTAGE OR CURRENT LOOP OUTPUTS ISOLATED OUTPUT

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