How to configure the Cisco ATA 186 with fax

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The Cisco Analog Telephone Adaptor (ATA) 186 supports fax transmission only as pass-through. It cannot support fax relay. Both ports of the ATA support fax calls. For fax calls to work correctly, both the Cisco ATA 186 and the supporting gateway must be configured correctly. On Cisco gateways, fax-relay is on by default. For the fax calls to work between the ATA and the gateway, the fax-relay on the gateway must be disabled. The Cisco ATA 186 sends fax by either fax detection method or recieve (Rx) and transmit (Tx) codec. In fax detection mode, the Cisco ATA 186 can be configured using the LBRC. The Rx and Tx codec modes negotiate any codec for voice calls until it detects a fax-tone. Once it detects the fax-tone it performs one of these tasks:

Turn off fax tone detection.
Turn off silence suppression.
Renegotiate the codec to G.711 u-law or G.711 A-law.

Note: The fax tone can be detected only for calls terminated by the ATA. For calls originated by the ATA, the fax detection and renegotiation of the codec has to be initiated by the supporting gateway. G.711 FAX Mode: In this mode, the Cisco ATA 186 simply passes the Real Time Protocol (RTP) packets sent between the end fax machines without intervention. It treats the fax session like any normal voice call. Note: Fax transmission rates are supported up to 9600 bps. For more information on fax transmission rates, refer to: Fax Passthrough Limitations on ATA 186 ATA 186 L1/L2 can support fax rates up to 14.4kbps. Note: ATA 186 is not supported for analog modem calls. The modem referred to throughout the documentation implies fax modem. For more information, refer to: Configuring and Troubleshooting the Cisco ATA 186 with Fax

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