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.
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?
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