Microprocessor Controller; Carrier Operated Switch; Voltage Regulator; Tuning Voltage Supply - RF Technology Eclipse Series Operation And Maintenance Manual

5 CIRCUIT DESCRIPTION

5.10 Carrier Operated Switch

5.9 Microprocessor Controller

The microprocessor controller circuit uses an advanced eight bit processor and several support
chips. The processor U15 includes EE memory for channel frequencies, tones and other
information. It also has an asynchronous serial port, a synchronous serial port and an analog
to digital convertor.
The program is stored in U12, a CMOS EPROM. U13 is an address latch for the low order
address bits. U11 is used to read the channel select lines onto the data bus. U7 is an address
decoder for U11 and U12. U14 is a supervisory chip which keeps the processor reset unless
the +5 Volt supply is within operating limits. U16 translates the asynchronous serial port
data to standard RS232 levels.
The analog to digital converter is used to measure the received signal strength, tuning voltage,
dc supply voltage and the carrier squelch setting.
5.10 Carrier Operated Switch
The carrier operated switch is an opto-coupled (IS01) output. Internal jumpers (JP4,7,8,9)
can be connected to provide loop source, loop switch, free switch and various other
configurations.
The C.O.S. can be set to active (switch closed) on carrier or active in the absence of carrier.
The generic term "Carrier Operated Switch" may be misleading in this case. If a sub-audible
tone has been programmed for the channel current channel, the C.O.S. will be controlled by
carrier and tone detection.

5.11 Voltage Regulator

The dc input voltage is regulated down to 9.4Vdc by a discrete regulator circuit. The series
pass transistor Q20 is driven by error amplifiers Q21 and Q22. Q23 is used to start up the
regulator and once the circuit turns on it plays no further part in the operation.
This circuit is short circuit and overload protected. It provides much better line isolation and
lower dropout voltage than can be obtained with current integrated circuit regulators.

5.12 Tuning Voltage Supply

U18 is an astable multivibrator. The output from pin 3 of U18 is a rectangular 8 volt
waveform with a frequency of approximately 200KHz. This output is connected to a voltage
tripler circuit consisting of C170-C173, D13 and D14 to produce +20Vdc. This is used by
the frequency synthesizer to provide tuning voltages up to +18Vdc.

6 Alignment Procedure

The following procedures may be used to align the receiver for optimum performance.
Normally alignment should only be necessary after repairs on that part of the circuit.
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RF Technology R800 Page 12