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7.5 Testing via DTE Interface Signals
The DTE interface (Appendix B) allows some tests to be controlled by
signals from the DTE.
In the factory default configuration, the facility is disabled. To allow DTE-
initiated tests, the command
&T12 must be set.
The modem's self-test facility cannot be used with the tests; the DTE must
be used to generate a test pattern and provide error-checking facilities.
7.5.1 Local Analogue Loopback
1. The modem's internal links must first have been set as described in the
Appendix entitled 'Technical Guide'.
2. Initiate the test by a signal (>
+
6 volts) on pin 18 of the DTE port.
3. Transmit a test pattern from the DTE. It will be passed round the loop
and returned to the DTE.
4. Check that the test pattern has not been corrupted.
5. Terminate the test by returning pin 18 to the low (< –6 volts) state.
7.5.2 Remote Digital Loopback
1. The modem's internal links must first have been set as described in the
Appendix entitled 'Technical Guide'.
2. Initiate the test by a signal (>
+
6 volts) on pin 21 of the DTE port.
3. Transmit a test pattern from the DTE. It will be passed round the loop
and returned to the DTE.
4. Check that the test pattern has not been corrupted.
5. Terminate the test by returning pin 21 to the low (< –6 volts) state.
7.5.3 Test State Indication
The test state can be indicated to the DTE by a signal from the modem on
pin 25. In the default state, pin 25 will go high whenever the modem is
performing a test, regardless of the method used to start the test. This can
be used to indicate to the DTE that the modem has entered test mode and is
not available for normal data transmission. (This output can be disabled
by a link change as described in the Appendix entitled 'Technical Guide'.)
X460-306851 Issue 1 7-8 Rev.0