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Community Member

Detect dial tone on FXO port before dialing

I have a UC500 system that has another device wired into the same phone line in parallel to the UC500.

I have discovered a problem if someone is tying the line up in front of (or in parallel) to the FXO port on the UC500, the UC will still pick up and use the port as though it were available.

Is there any way to have the UC check for dial-tone before attempting to use an FXO port? Or is there another way to check for the line being in use?

Here is my configuration:

trunk group PSTN
hunt-scheme sequential both down

voice-port 0/1/0
trunk-group PSTN
echo-cancel coverage 64
connection plar 199
caller-id enable
!
voice-port 0/1/1
trunk-group PSTN
echo-cancel coverage 64
connection plar 199
caller-id enable
!
voice-port 0/1/2
trunk-group PSTN
echo-cancel coverage 64
connection plar 199
caller-id enable
!
voice-port 0/1/3
trunk-group PSTN
echo-cancel coverage 64
connection plar 199
caller-id enable
dial-peer voice 50 pots
trunkgroup PSTN
destination-pattern 9T
no sip-register

3 REPLIES
Community Member

Re: Detect dial tone on FXO port before dialing

This is a good question. I am pretty sure we do not do actual dialtone detection. We just implement a timer after going offhook to send digits. Now, if the port is offhook, we should detect this. Are you using a line splitter? What is your wiring like? This is usually not recommended, but it should work.


Marcos

Community Member

Re: Detect dial tone on FXO port before dialing

Marcos,

Thanks for the prompt reply.

I understand and agree that line sharing is not a recommended setup, but like you, I agree it should work, too. We are using a line splitter. The phone line comes out of the telephone termination point and into the splitter. One side of the splitter goes to the UC and another side gets plugged into a credit card machine. The credit card machine isn't used that frequently, so this isn't much of a problem, but there are cases where the line is in use and then the UC tries to grab the line to place the call. The user on the IP phone hears the analog modem conversation.

Ideally, I would like the UC to check the status of the port before dialing. If its in use, I would like it to keep descending down the ports in the trunk group until it finds an available line.

You think increasing the "pre-dial-delay" command under the appropriate "voice-port" may achieve the desired effect?

Thanks,

--Mike

Re: Detect dial tone on FXO port before dialing

Do you have an FXS port available on the UC500?  That would solve the problem as well.

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