Microwave Data Systems MDS 4310, Installation, Operation & Field Maintenance

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2-8 INSTALLATION MDS 05-2415A01, Rev. A
PIN 6: DSR—Data Set Ready
Provides a + 8 Vdc DSR signal to external terminal through a 1 k
Ω
resistor.
PIN 7: Signal Ground
Connected to ground (negative supply potential) at the radio PC board.
PIN 8: DCD—Data Carrier Detect
with internal modem
Provides an RS-232 compatible output. Goes “high” when the modem detects a
carrier from the master station.
PIN 9: Transmit Audio Input
without modem
The transmit audio input pin is normally connected to the audio output from the
associated modem or RTU. The input impedance is 600 ohms, and the deviation is
factory set so that an input level of –10 dBm produces a nominal transmitter
deviation of 2.5 kHz. This is the correct deviation level for most 12.5 kHz systems
and will also provide satisfactory service in most 25 kHz systems.
The deviation can be adjusted to fulfill the requirements of equipment using audio
levels other than –10 dBm. See Chapter 3—Field Tests And Adjustments for
detailed alignment procedures.
If the distance to the modem or RTU is greater than five feet (1.52 meters), use a
twisted pair of conductors to connect the transmit audio circuit. Connect one end
of the pair to the audio output terminals of the modem or RTU and the other end
to Pin 9 and Pin 7 of the
INTERFACE
connector.
with internal modem
The order wire audio output appears on Pin 9 whenever the external order wire
assembly is connected. Transmit audio from the modem is cut-off internally
within the transceiver when order wire is in use. This applies only to
PTT
.
PTT
will not cut off the internal modem output.
PIN 10: Receiver Unsquelched Sense
This pin is not used in typical installations, but it is available as a convenience for
special applications. It is pulled up to +8 Vdc through a 1 k
Ω
resistor whenever
the receiver squelch is open, and pulled down to less than 1 Vdc when the squelch
is closed. The output resistance of 1 k
Ω
should be considered when interfacing
external equipment.
PIN 11: Receiver Filtered Audio Output—Line Level
This is the received audio output of the transceiver and is connected to the audio
input of the external modem or RTU. It will drive a 600 ohm load; the output
level is factory set to –10 dBm into 600 ohms for rated system deviation of
2.5 kHz on the received signal. Audio from the receiver discriminator is passed
through a 3 kHz low-pass filter before it reaches this pin. This response is ideal
for most external modems because it eliminates high frequency noise that can
degrade the bit error rate performance of the modem. The audio response is nearly
flat between 50 and 3000 Hz (no de-emphasis).