Commercial In Confidence
33
The RSSI signal is represented by a voltage from 0-5VDC
3
TX LED
The anode of a transmit LED may be connected to this pin and its
cathode should be connected to ground, the LED supply current
will be approximately 3mA so a low current LED should be used.
The LED will illuminate whenever the CMD400 enters transmit
mode.
4
BUSY LED
The RX LED connects in the same way as the TX LED above and
provides an indication of carrier detect.
5
DI
0
/TXe
Digital input 0 (0 – 30VDC) or TX enable in Audio mode
6
DI
1
Digital input 1 (0 - 30VDC)
7
DO
0
Digital output 0, open collector
8
DO
1
Digital output 1, open collector
3.15
EXTERNAL AUDIO PATH
The selection of internal modem or external audio operation is made at the time of
programming the ART. If programmed for external audio the external modulation input and
output will provide an adjustable range of +3dBm to -20dBm into 600 ohms, this adjustment
is made by electronic potentiometers under the control of the set up program. The external
RX audio is optionally muted in the absence of a carrier. The external audio input and output
is via isolating transformers and so will couple directly to almost any 600 ohm interface.
In the external audio mode there are two options for keying the transmitter; first using digital
input 0 (marked DI0/XPTT on the front panel), or secondly by using the tone operated
switch (TOX). The TOX can be programmed to key on either V23 mode 2 or Bell 202 tones.
Other tonesets can be provided for, by special order.
It should be noted that the external audio path is AC coupled and so is not suitable for GMSK
or multi-level signalling at baud rates above 2400 baud.
3.16 INTERNAL
MODEM
The internal modem can operate at speeds between 150 and 9600 baud, at speeds up to 1200
baud FFSK signalling is used with either Bell 202 or V23 mode 2 tone sets. 2400 baud uses a
1200/2400 Hz coherent FFSK tone set, 4800 baud uses GMSK, and 9600 baud uses four level
FSK. All of these tone sets with the exception of 9600 baud are compatible with the
Communique CMD400 radio, in addition the V23 tone set is compatible with many older
systems from other manufacturers.
