User Manual

TR-800 Service Manual
-11-
 Circuit Description
Repeater Communication Interface & Display Unit
Theory of Operation
Setup/Knockdown (U0107D, Q0101, Q0103, Q0106, Q0107 and Q0108):
The Setup/Knockdown state at power-up can be configured via HR-800 programming software. The
electronic switch, Q0106 and Q0108, causes the Setup/Knockdown action by applying or removing
voltage at the ignition control, pin15, of “J0102-Main”. After power-up, the Setup or Knockdown state
may be changed remotely with a signal from pin10 of “J4-Slave” or locally through the front panel
SETUP. S0102 is a momentary contact switch that is debounced by the Q0103/Q0107 latch circuit. The
orange “SETUP” LED, CR0102, illuminates to indicate the Setup state.
As the Setup/Knockdown circuit goes from the Knockdown to the Set-up state, Q1 is momentarily turned
on by Q0108 via the C0101/R0103 timing circuit. The push to talk (PTT) input of the slave radio, pin8 of
“J4-Slave” is pulled low by Q0101 and keys the transmitter. The “Rx” LED, CR0105, will briefly flash
during the moment that Q0101 is conducting.
Forward Audio Routing (U0103A, U0104A, U0104D and U0105A):
The audio gate, U0104D, quarter of an analog switch BU4066B, enables and disables the audio from
front panel MIC audio input. U0104D is turned on with an active dc level high driven at the output of
NAND gate U0103A-3 by the front panel PTT input. The salve radio audio output from pin5 of
“J0104-Slave” is routed to a potentiometer, RV0101. The output of RV0101 is applied to another switch
U0104A. U0104A is enabled once a valid signal is received and will route the audio to transmitter. The
external audio input, ACC Relay audio, is routed to another potentiometer, RV0103. The output of
RV0103 is applied to the second half of U0105, an operational amplifier NJM2904. U0105A, R1106 and
R0118 make a buffer amplifier for the link audio. All the “forward” audio will mix together and route
through S0101-5 to the main microphone transmitter audio, pin2 of “J0106-Main”.
Reverse Audio Routing (U0104B and U0104C):
Part of front panel MIC audio is routed to the input of U0104B, quarter of the analog switch BU4066B.
The output of U0104B is also controlled with an active low input by the front panel PTT. Audio present on
pin5 of “J0102-Main” is routed through S0102-7 to a potentiometer, RV0102, which is used to adjust the
audio level for proper deviation. As with the forward direction, the audio output of RV0102 is applied to
an analog switch U0106A. This switch turns on only if a valid signal is detected and pin6 of U0104 goes
high.
Forward and Reverse Key-up (Q0102, U0103, U0107, Q0105, Q0111 and Q0116):
When a valid input signal is present at the slave radio, pin6 of “J0104-Slave” will be pulled low and turn
off Q0105 through two NAND gates, U0107B and U0107C, along with RPT enable trigger. A dc level
high output from Q0105 will be applied to pin37 of U0110 and keys the main radio PTT through output
from pin12. The red “Tx” LED, CR0106, illuminates.
When the reverse key-up function is enabled, as in the bi-directional repeater configuration, S0101-8
must be on. Q0116 is a dc amplifier (buffer) for the Rx Carrier signal from pin6 of “J0102-Main”. An active