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Cisco ATA 186 and Cisco ATA 188 Analog Telephone Adaptor Administrator’s Guide (SCCP)
Ol-3141-01
Chapter 6 Configuring and Debugging Fax Services
Debugging the Cisco ATA 186/188 Fax Services
Debugging FAX Pass-through Mode
When the Cisco ATA is configured to use fax pass-through mode, the fax call session can be established
with an arbitrary voice codec. Once the voice call has been established, fax machines can signal their
presence by means of a CED tone or V.21 preamble flag, after which the gateways send NSE packets to
initiate switchover.
Note For fax pass-through mode, check the Cisco ATA debug log to verify that it is acting as an originating
gateway as well as a terminating gateway.
Terminating-Gateway Example
When the Cisco ATA is used as a terminating gateway for a fax session, make sure the following
conditions are true:
• The Cisco ATA transmits CED-tone-event NSE packets.
• The encoder switchover to G.711 occurs during the NSE-packet transaction.
An example debug log for a terminating gateway scenario is show below:
[0]Tx MPT PT=100 NSE pkt c0000000
[0]codec: 4 => 0
[0]Rx MPT PT=100 NSE pkt c0000000
Note The NSE response to the CED tone event is not mandatory; some gateways may not send back an NSE
response.
[ch] codec: <pt1> => <pt2> Voice codec switchover occurred. The voice encoder type switched from
pt1 to pt2 for the channel ch.
For example,
[0]codec: 4 => 0 indicates that the local voice encoder
on the Cisco ATA switched from G.723.1 to G.711µ-law.
[ch] Rx MPT PT=<NSEpt>
NSE pkt <event>
Channel ch received an NSE packet of event with payload type of NSEpt.
For event, c0XXXXXX indicates a CED tone event, and c1XXXXXX
indicates a phase reversal event.
For example,
[0]Rx MPT PT=100 NSE pkt c0000000 indicates that the
Cisco ATA received a CED tone event NSE packet with payload type of
100.
[ch] Tx MPT PT=<pt> NSE
pkt <event>
Channel ch transmitted an NSE packet of event with payload type of
NSEpt. For event, c0XXXXXX indicates a CED tone event, and
c1XXXXXX indicates a phase reversal event.
For example,
[0]Tx MPT PT=100 NSE pkt c0000000 indicates that the
ATA transmitted a CED tone event NSE packet with payload type of
100.
Table 6-2 Debug Log Examples (continued)
Log event Description