FXO to MJ unable to break dial tone

bgarczynski · Post by **bgarczynski** » Wed Mar 25, 2009 6:57 pm

I have a Cisco 1760 router with 2 FXO interfaces, on connecting to the magic jack. When I place an outbound call the FXO to MJ goes off hook but no DTMF (tones) are passed into the magic jack. I can tell that MJ detects the FXO going off hook because the softphone pops to the front of the screen. When the FXO port goes off hook the MJ plays dial tone back to the phone but I am unable to break the dial tone as no DTMF seems to be getting to the MJ. A regular analog phone directly connected to the MJ works just fine. I am trying to use the MJ to simulate a regular POTS line for lab use. I have messed around with gain/impedance/DTMF Relay but I have not been able to get DTMF to the MJ. Incoming calls from the MJ to the FXO port work just fine. Any help is greatly appreciated.

mberlant · Post by **mberlant** » Wed Mar 25, 2009 10:11 pm

Does the Cisco work well when connected to a real POTS line? If so, you may need to go into the Cisco Manager and make a change. It has been well over 10 years since I have played with that IOS, so I don't know if this advice is workable or not.

POTS uses a -48VDC battery, but the MJ dongle supplies a -24VDC battery, which is sufficient to drive most modern phones. The Cisco may be set to require a -48VDC battery in order to recognize the line. Look for two things in the Cisco. First, look to see if the Cisco is reporting "Line in Use" when the MJ is in fact idle. If so, look for a parameter named "Line-in-Use Voltage", or similar. It is probably set to 22V. Change that setting to 12V and see if the Cisco doesn't start seeing the MJ as alive and available for use.

Please let us know how you fare.