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New Member

incomming PSTN call to FXO

I have setup a h.323 router and have callers who will call but the router seams to wait untill the call has rung for 2 to 3 rings before it accepts the call.

I have looked that the LED light on the FXO and I can see it light up but the call does not get picked up untill two or three rings later.

voice-port 0/0/0

trunk-group FXO-PORTS 1

timeouts call-disconnect 1

connection plar opx 1700

caller-id enable



dial-peer voice 1700 voip

destination-pattern 1700

session target ipv4:

incoming called-number .

dtmf-relay h245-signal



Re: incomming PSTN call to FXO

the only thing coming to mind is the ring number command. if you didnt adjust it then it should be set to 1 which is the default. the only other thing based on my limited experience is that i normally use connection plar xxxx and not opx xxxx.

ring number number

no ring number number

Syntax Description


Number of rings detected before answering the call. Range is from 1 to 10. The default is 1.

Cisco Employee

Re: incomming PSTN call to FXO

This is happening becuase you have caller id enabled on the voice port. Caller ID is sent as a burst of FSK modem tones between the first and second rings, so the voice port waits until the caller ID has been recieved before setting up the connection plar call leg. This is why it takes at two least PSTN ring cycles before the IP leg starts to ring.

New Member

Re: incomming PSTN call to FXO

great info.

i have always wondered why this happens, i have customers same configuration, default (ring number 1) and caller id enabled.

some customers it waits two rings for the AA (using connection plar) to work and others straight away.

i guess this means the latter is receiving the caller id faster!!!

Good day

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