Diagnostics, Local Analog Loopback Figure

13.DIAGNOSTICS

The following pages provide hardware techniques for diagnosing communication problems and thereby isolating the problem at the local modem, the remote modem or the interconnecting line.

(a)LOCAL ANALOG LOOPBACK (Figure 2)

Requires a loop back cable with a built-in circuit for line loss to simulate a typical leased line condition (See Figure 3).

Connect the loop back cable to the RJ11 connector on the modem under test.

Set Dip Switches as follows…

Switch 7 = OFF 4-Wire
Switch 9 = ON	Soft Carrier Turn Off Enabled
Switch 1 = ON	Transmit (TxA) Signal Level = 0dBm
Switch 3 = ON	Receive (RxA) Signal Level = –33dBm
Switch 6 = OFF Switched Carrier
Switch 4&5 = ON	RTS/CTS Delay = 50ms

Test 1: RTS/CTS Analog Control

Set RTS “ON” and check that CD (Carrier Detect) turns “ON”.

Turn RTS “OFF” and ensure that CD turns “OFF”

With RTS “ON”, run a test message at TxD and verify that the same message is received at RxD with no data errors.

Test 2: Transmit Signal Power & Receive Levels

Set Dip Switch 1 OFF (TxA = -10dBm)

CD will be OFF.

Change Dip Switch 1 to ON (TxA = 0dBm)

CD should now be ON.

MIU202T Installation, Operation & Diagnostics Edition: April 4, 1998

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