Nortel DMS-100 Series Maintenance Manual page 397

16 The SMS sends a request to the RCS for a reverse battery test and scans
for off-hook. If there a positive talk battery is present, the following
actions occur. The RCS detects off-hook and sends off-hook A-B bits to
the SMS.
17 The channel loss test uses the TTU to determine if the correct
termination occurs.
18 The SMS sends the RCS a message to remove termination.
19 The SMS signals the RCS to test coin return. The RCS connects the
reflect-NTPG termination and sends coin ground A-B bits as off-hook.
The RCS sends bits as off-hook if the channel unit provides negative
coin control voltage.
20 The SMS requests the RCS to run negative coin check. The RCS sends
coin ground A-B bits.
21 The SMS sends negative loop mode A-B bits while the TTU conducts
channel loss test.
22 The SMS sends the RCS a message to terminate the channel test.
23 The diagnostic is terminated.
To remove a test termination, the SMS sends the RCS an on-hook message
in the M-field of the DDL. To halt a continuous test, the SMS or RCS can
send test alarm message in the M-field of the DDL.
Using external test equipment
When you use external test equipment to test a line, a bridge connection to
the line is set up. The bridge is set up with a conference circuit when the
line is in the talking state. If the line is idle, test equipment connects to the
line through the MTA network. This bridge connection enables operating
company personnel to verify that the line is in use.
The following figure shows an example of bridged access to a subscriber
line that extends from an RCS:
DMS-100 Family SMS Maintenance Manual XPM10 and up
Trouble isolation and correction 9-33