5902 Bell 202 Modem Hardware Manual
October 19, 2007
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5.4.1
Full Duplex Point-to-Point Systems
Unless noted otherwise, all switch settings apply to both modems.
1.
Wire both modems using four wires as described in section
4.2-Field Wiring
.
2.
Open all switches on both modems. Close the FDX and 4W switches on both modems.
3.
Turn on power to the system. Observe that the KEY LED is illuminated on both modems,
indicating that they are transmitting carrier. If is it not, confirm that the FDX switch is closed
and that power is applied. The KEY LED must be illuminated on both modems for operation.
4.
Confirm that the CD LED is illuminated on both modems. If it is not, check that the transmit
pair from each modem connects to the receive pair on the other modem. If a CD LED flickers,
confirm that the other modem’s transmit gain is normal (see section
6.1-Gain Adjustments
) and
that the wiring is solid.
5.
Attempt to communicate. The devices should communicate without problems. If you need to
slow down communication, reconfigure your DTE for half duplex, and lengthen the RTS/CTS
delay (adjust the close CS0 and CS1 switches). This inserts a pause before each transmission. If
your DTE does not support half duplex, RTS/CTS control, you can use the F Option module.
This module provides RTS/CTS handshaking for a full duplex DTE.
6.
Install the system in the field.
7.
Confirm that the CD LEDs on both modems are steadily illuminated. If they are not, the
received signal is intermittent, noisy, or too weak.
5.4.2
Half Duplex Multi-Point Systems
Unless noted otherwise, all switch settings apply to all modems.
1.
Wire the system as it will be used in the field as described in section
4.2-Field Wiring
.
2.
Set the 2W and 4W switches according to the number of wires used.
3.
Set the FDX switch according to the system configuration you have chosen. See the sample
configurations above for suggestions.
4.
Close the RCD switch if you are using the radio frequency carrier detect input. Open the switch
if you are not.
5.
Close switches CS0, CS1, SC0, SC1 and CSH.
6.
Close switches CL0 and CL1 if the modem is used for constant carrier reception.
7.
Open all other switches.
8.
Turn on the system and attempt to communicate.
9.
Observe the CD LED on receiving modems. It should illuminate when the transmitting modem’s
KEY LED is illuminated. This indicates that the receiving modem hears the transmitting
modem’s carrier. If the CD LED does not illuminate, try the following, and repeat this step.
Confirm that the wiring is correct and that the transmit signal from the transmitting modem
is connected to the receive signal wiring on the receiving modem or modems. One of the
easiest ways to test the communication path is to temporarily put the transmitting modem
into full duplex by closing the FDX switch. All receiving modems should have a
continuously illuminated CD LED. If they do not, the system will never function.
If the system uses radios, confirm that all radios are using the same frequency. Try adjusting
the squelch level on the receiving modem.
10.
Observe the CD LED on receiving modems. The LED should turn on solidly when carrier is
received, and turn off solidly when the transmitting modem turns off its KEY LED.
