TSS Commands
Two commands can be initiated by the 3745 TSS (FESA) to test the LIC type 6:
CCITT loop 3 (with or without line wrap block)
Self-test.
CCITT loop 3
This test is initiated by the 3745 TSS (FESA) on the DTE interface.
It is the same as for LIC type 5. See page 4-71.
Self-test
This test is the same as for LIC type 5. See page 4-71.
DDS Loop
This test is initiated by the DDS link via a bipolar code violation or a DC line current
polarity reversal, as defined in the preliminary
ATT PUB 62310 dated September
1983. It consists in a wrap at the DTE interface:
1. Detect bipolar code violation or current polarity reversal
2. Raise TI
3. Set 'modem busy' bit ON in DTE registers
4. Drop CD and RFS, DSR kept ON
5. Force data to 'mark' at the host side, while looping back data from DDS
6. Detect end of bipolar code violation and current polarity reversal
7. Drop TI and reset the 'modem busy' bit.
The test lasts as long as a code violation or polarity reversal is detected. It runs
only if the LIC type 6 is in operate mode.
Alarm Tone Detection
A failure signal is sent when a hard internal failure is detected, provided that
'network services' are enabled. This signal contains in a long sequence of bipolar
zeroes.
However, LICs type 6 detect both:
Remote power OFF tones
Remote failure tones.
Tone Characteristics
Speed
data speed
Duration
Power OFF
126 zeroes
Failure
252 zeroes
End-to-end passthrough delay
varies from 32 to 64-bit times depending on the configuration.
Tone Reception
The LIC type 6 receiving the alarm signal detects the alarm pattern and interprets
the information as a remote failure or power OFF.
This information is kept in storage and is reported to the NCP on request.
Chapter 4. Transmission Subsystem (TSS)
4-87
Summary of Contents for 3745 Series
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