Operating instructions

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7.4.14 Test Microphone Input
200Ω
dynamic, with PTT
7.4.15 External Tone Input
Compatible with all RF Technology receivers. Each unit is factory
configured to give
20% of maximum deviation for
an external tone input of 129mV.
7.4.16
T/R Relay Driver
An open drain MOSFET output is provided to operate an antenna change over relay or
solid state switch. The transistor can sink up to 250mA. A
1W flywheel diode connects
to the 12V rail to prevent damage to the FET from inductive kick from a relay coil.
7.4.17 Channel Select Input/Output
Coding - 8 lines, BCD coded 00 – 99
; illegal BCD codes used to encode channels
100 – 255.
If the MSN (Most Significant Nibble) is greater than 9, then the channel number is
defined by the formula:
16*MSN + LSN;
where the LSN is the Least Significant Nibble.
If the MSN is less than 9, but the LSN is greater than 9, then the channel number is
defined by the formula:
10*LSN+MSN;
Logic Input Levels - High for <1.5V, Low for >3.5V
Internal pull up resistors select channel 00 when all inputs are O/C.
7.4.18
DC Remote Keying
An opto-coupler input is provided to enable dc loop keying over balanced lines or local
connections. The circuit can be connected to operate through the 600Ω line.
7.4.19 PTT in
An external input that when “grounded” with at least 1mA of current, will cause the
exciter to key up. The current is drawn from the PTT in
input which attempts to “pull
up” anything that “grounds” it. It can be “grounded” with a short to 0V, or any
resistance up to 3.9k ohm. If the resistance of the “ground connection” is less than 2.2k
ohms, then up to three diodes in series can be part of the grounding path. This allows
systems installers to use quite complex diode logic to enable or disable exciters.
It would normally be “grounded” by the COS output of a receiver.
7.4.20 Programmable No-Tone Period
A No-Tone period can be appended to the end of each transmission to aid in eliminating
squelch tail noise which may be heard in mobiles with slow turn off decoders. The No-
Tone period can be set from 0-99.9 seconds in 0.1 second increments.
7.4.21 Firmware Timers
The controller firmware includes some programmable timer functions.
Repeater Hang
Time(Transmit Tail) - A short delay or ``Hang Time'' can be
programmed to be added to the end of transmissions. This is usually used in talk
through repeater applications to prevent the repeater from dropping out between mobile