Bell 5902 Hardware Manual page 44


To get a preliminary indication of proper operation in a half duplex application, perform the test
described in 6.2.2-Tone Transmission Test.

To test the modem by itself, perform a local Loop Back test. Configure the modem for full
duplex, four wire mode. Place the TST switch in normal mode. Connect the transmit (TX)
output to the receive (RX) input (see below). Using a computer or terminal on the DTE port,
transmit data to the modem. The data should be echoed back by the modem.
The transmit output can be connected to the receive input in two ways.

Select 2 wire operation to loop the signal back internally. Close the 2 WIRE switch and open the
4 WIRE switch. This does not test the line isolation transformers.

Select 4 wire operation to loop the signal back externally. Open the 2 WIRE switch and close
the 4 WIRE switch. Connect the transmit (TX) output to the receive (RX) input with external
wiring. This tests the line isolation transformers.
If these tests indicate the modem is not operating correctly, contact Control Microsystems for further
assistance.
5902 Bell 202 Modem Hardware Manual
October 19, 2007
43