Modem calls fails with ATA 186

Unanswered Question
Mar 4th, 2010

I have two ATA 186's registered to a Callmanager V7.1.  We are located in the UK.  When I plug a modem into the ATA,  I get dial tone, the device dials, . and the modem handshake begins.  The handshake caries on for some time until the other side hangs up.  If I plug the modem into a reguar analogue line the call goes through just fine.   There is obviuosly a setting that is not correct, however I don't see anyway to adjust impedance or anything.  Why isn't this working and how can I fix it?  Thanks for your help.

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Jaime Valencia Thu, 03/04/2010 - 11:39

User is unable to connect ATA to modem

Connecting a modem to the ATA is an unsupported hardware configuration and can have undesirable results. The ATA 18x is not designed to work with either PBX or KSU, or any other device except, plain old telephones because it does not provide Sup Disc parameters and it is expecting the end-device (an analog phone) to be hung up manually.



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ed.crawford Fri, 03/05/2010 - 01:45

Thanks for the information.  Does the VG2XX support fax and modem?

Jaime Valencia Fri, 03/05/2010 - 06:38

Cisco VG 224, VG 204 and VG 202 Analog Phone Gateways

The Cisco VG 224 (Figure 1), Cisco VG 204 (Figure 2), and Cisco VG 202 (Figure 3) are Cisco IOS®

Software-based analog voice gateways. The Cisco VG224 is a high-density 24-port gateway, and the Cisco VG 204 and Cisco VG 202 are low-density 4 and 2 port gateways, respectively. These gateways connect analog phones, fax machines, modems, and speakerphones to an enterprise voice system based on Cisco Unified Communications Manager (Figure 4). Having these devices tightly integrated with the IP-based phone system is advantageous for increased manageability, scalability, and cost-effectiveness. Commercial businesses can also use the Cisco VG 224, Cisco VG 204 and Cisco VG 202 with Cisco Unified Communications Manager Express to effectively augment an integrated services router (ISR) environment (Figure 5). Either topology environment will support business needs, ranging from high to low concentration of analog voice ports for modem calls, fax calls, and analog supplementary services.

Fax and Modem Connectivity

The Cisco VG 224, Cisco VG 204 and Cisco VG 202 support fax machines and modems. When using fax machines, they support Cisco fax relay, T.38 fax relay, and fax passthrough. Cisco or T.38 fax relay technologies allow transfer of faxes across the network with high reliability using less bandwidth than a voice call. All modems can be connected to the Cisco VG 224, Cisco VG 204 and Cisco VG 202 and will be transferred over the network using modem passthrough.



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Hi Jamie,


We are putting in VG202XM devices into our Stores to run both the Fax Machine line and the Alarm Panel modem line.  We are doing this in order to be able to cancel the two old fashioned telephone lines from the carrier, per Store, to save costs, and the carrier is making them end of life in some places of Australia.

We have configured the VG202XM device for MGCP and the two ports are POTs. We also ensured that the Region in the Device Pool on CUCM (Version 8.6) has G.722/G.711 so therefore no compression for the call going to the nearby ISDN Gateway (with 64K timeslots).  The Fax machine works perfectly through the VG202 however the Alarm Panel that dials up to the Security Depot concentrator is not working very well, and the concentrator hangs up the call.  Out of 20 calls only one remained connected and held up. If we put the Alarm Panel back to the old Telephone line it works perfectly, so its just not happy to connect via the VG202, but the Fax Machine is.


Any ideas?





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