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Testing the Local Modem
Test local operation with the modem offline in command mode. Use
LAL and LAL/TP to test the local modem and the communications to
the local DTE.
Note
Figures 7-1 through 7-5 include LED test indications. These
indications are valid when DTE options are set by factory
option set #1 and RTS is active from the DTE. Where
indicated, RD and/or TD may be on, off, or flashing
depending on the type of DTE and its operating state.
Local Analog Loopback — &T1
In Local Analog Loopback the modem transmitter connects to its
receiver so the analog signal normally sent over the telephone line is
received locally.
If operating on leased lines, the lines are terminated into 600 ohms
(Figure 7-1). If off hook on a dial-up line, the modem is forced on hook.
Figure 7-1. Local Analog Loopback
(4-Wire Operation and 2-Wire Operation)
For 2-wire operation, Analog Bilateral Loopback is invalid. In 4-wire
operation, Analog Bilateral Loopback connects the receive line to the
transmit line through a buffer amplifier.
Test the local DTE and cable by entering the &T1 command. Enter a test
message and verify it is echoed on the screen. If it is not returned
exactly as entered, the terminal equipment or data cable is at fault.
V.3600
Test Mode Operation
7-3
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