We have a customer who has some emergency phones around their campus. These are made by Ramtel, and are simple devices on a pedestal, w/ two buttons, black and red. Typically, one dials security and the other dials 911, though we currently have both programmed to dial 911. You program the device by dialing into it. The device is programmed properly.
When hitting the black button, and plugged into the VG248, it dials out properly. When hitting the red button, plugged into the vg 248, we hear dialing then disconnect. (Note: this is not a PLAR device, it must dial the digits.) Ramtel suggested that we test the voltage. The VG248 provided 35 volts on-hook. We found we were getting only 8.8 volts off-hook. Ramtel advised that the device must have 10 volts off-hook to work properly. We decided to switch to an FXS card on a 2811 to see if it would push more voltage. The on hook voltage was then 48 volts and the off-hook voltage was approximately the same 8.8 volts; however, now we get both buttons to dial and then disconnect about a second later. We've tested the lines and they are clean.
When we plug the device directly into a POTS line, it works as expected, so it looks like the voltage is definitely an issue. It appears that these devices have a very low tolerance for variance in expected voltage.
What is more troubling is that these devices were plugged into a CM 4.x system on the same VG248 and reportedly worked previously. Unfortunately, I was not able to verify that, but that is the story I have heard.
Has anybody fought these before? Is there anything I can do to increase the voltage? Is there any device that would increase the voltage pushed out?
I've actually found with the ramtel call boxes the alt-battery command does help some (goes from not working to works most of the time). For the price of the ring boosters we can buy call boxes that don't require an abnormal amount of voltage like a Talkaphone.