Showing results for 
Search instead for 
Did you mean: 

Analog Emergency Phone Voltage Problem

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?


Accepted Solutions

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.

View solution in original post


You may want to look into the new VIC3 third-gen voice cards. They have introduced a number of more high-voltage capabilities for legacy devices such as this.

It is probably worth opening a TAC case to make sure that it's just a voltage issue - if this device automatically dials DTMF you may have an issue with your DTMF relay, or various other problems.


Thanks, I will run this by TAC.

We also discovered ring and loop voltage boosters which we are going to try in-line. If anybody ends up in this boat, search for "Loop Current Booster" and you should find an option on I'll post again when we have had a chance to test this device.

I'm having an almost identical problem. These boxes were working fine (on vg224) and then one day they all decided, nope. We've discovered a lot of things.

#1 The version of code we were running was only putting out 22 volts max

#2 There is an undocumented command "alt-battery-feed feed2" applied to the port gives another 7-8 On hook Volts on the line

#3 Even ATT's line does not meet ramtel's spec

Ramtel's spec says on hook voltage has to be between 40 and 50V and off hook voltage has to be 10V with a minimum of 30ma current, max 55ma

I've tested the VG's with and without the alt-battery command and an ATT line and the only difference is ATT is putting out 46V and the VG maxes at 43-44. Everything else is identical (26ma on hook, 6V 12ma off hook). I'm going to call ramtel and see what they believe is going on since the voltage is in spec and the current is the same as what ATT is providing.

Sorry, I need to correct myself. I got to thinking about how I tested current and realized I had hooked it up wrong. I just retested the off hook current, and the VG224 puts out 22ma standard, 25ma with the alt-batter, and ATT puts out 26ma. So still outside of ramtels spec

Sometimes for legacy devices 3rd party 'ring boosters' or other voltage increasing devices become necessary.

There are some hidden commands for voltage, but I haven't found any of them to be useful personally.

If you have access to a VIC3 2 or 4 port FXS card you can try your luck there.


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.

Thanks for the input. It looks like the "alt-battery-feed feed2" command is only available on 224s and IADs, unfortunately it won't take on a 2800. I will try the booster and look at the other make of phone you mentioned, as long as TAC doesn't have any better ideas for me.

I'll be interested to know how it turns out. I guess the only thing I haven't been able to explain is why they were working before and now they're not

I'll post whatever solution we arrive on.

I think the answer to that is that only the black button was typically tested before, but that's just a guess. In other words, it wasn't working before, and likely wasn't regularly tested.

Thanks again for your feedback. Before these posts, it looked like no one else had the pleasure of dealing w/ Ramtel.

I took jbf's advice and went w/ a Talkaphone which worked perfectly.  We did discover that Ramtels are great for target practice, not so good for IP telephony.



hopefully this saves someone some trouble.

with Tac`s help we were able to get a Ramtel R733 two button phone to call out.

heres the config im using.  this is on a vg224 on  SCCP,

voice-port 2/5
timeouts initial 60
timeouts interdigit 60
timeouts call-disconnect 0
timeouts ringing infinity
timing hookflash-in 1550 150
caller-id enable
no battery reversal
alt-battery-feed feed2
no shut

Recognize Your Peers
Content for Community-Ad