User's Manual Part 6
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For standard mobiles in normal operation, the audio mute elements, transmit inhibit
and opto driver are all inhibited by the auxiliary control. The radio can be used nor-
mally with ‘auxiliary off’, and line controlled with ‘auxiliary on’.
With ‘auxiliary on’, the line output mute elements and opto driver are controlled from
the RX-GATE. A signal on the BUSY line inhibits the transmitter line key circuitry. Line
derived key signals, such as OPTO-IN, KEYING and PTT-IN, can be used to key the
radio, provided the auxiliary control is on and the radio is not busy.
The KEYING line is used for back-to-back control of two radios, each with a line inter-
face PCB. This enables crossband linking to be achieved with a minimum of external cir-
cuitry. In this case, the KEYING line can be linked to the OPTO-IN line on each unit,
with a wire between the two OPTO-IN lines providing bi-directional control. KEYING is
controlled by the receive gate and is used to drive the opto input of another line inter-
face PCB.
The opto input is intended to be connected to the output of an optocoupler circuit (BJT)
used for loop and tail keying via transmission lines (refer to Section 8.14.6, “Applica-
tions”).
The opto output is intended to be connected to the input of an optocoupler circuit (LED)
used for loop and tail keying via transmission lines (refer to Section 8.14.6, “Applica-
tions”). The sense of this circuit can be changed by a link.
An adjustable time delay circuit is available to prevent transmitter cycling when cross-
band connected radios are both operating on repeater channels. The circuit is adjustable
to approximately 1.5 seconds, with the time delay control fully clockwise, and can be
disabled completely by removing a link.
PTT-IN can be used to key the transmitter. Links are available to enable either logic
sense. For trunked versions using modems, a circuit is provided to set up a call automat-
ically.
Control logic for telemetry and modems is provided so that the radio can be operated
automatically. IN-LOCK-OUT, BUSY/GATE and TX/RX-OUT outputs can be set by
links for either logic sense.
Trunked modems operate in a different manner, and first have to set up a call to obtain a
traffic channel allocation.
Logic is available which requires several link changes, as some of the radio options con-
nections perform different functions:
Standard Trunked
AUX on/off not clear to send
emergency external call request
call traffic channel allocated