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VoIP with Analog PA Systems and Visual Alerts?
An anonymous reader asks: "We have an Asterisk/SIP based VoIP system at work, and I've been tasked with adding some features. First, we need to be able to patch it into our analog PA system at several office locations. I've managed to hack together a polycom phone set to auto-answer, and a custom cable from the handset to plug into the PA. This works well enough, but the phone really isn't designed for it, and I find that it just isn't reliable. What I need, and haven't been able to find, is a simple SIP enabled device that will auto-answer, and has line-out that I can feed to the PA. That way, if a user calls one of several numbers, they get tied into the associated PA system, or maybe even all PA systems at once. The next piece of the puzzle is a visual alert so that when a SIP phone is ringing, a light flashes. This will allow people in a loud environment to still know the phone in the office is ringing." Any ideas as to how this could be done?
"Ideally this would be just another SIP device that I could have Asterisk dial the same time the office phone gets dialed. The analog version of these is easy to come by, but I haven't been able to find a networked SIP version anywhere.
I'm not above building my own if their are some basic SIP device schematics out there, but I'd rather find a commercial solution and be done with it. Any help will be greatly appreciated."
I'm not above building my own if their are some basic SIP device schematics out there, but I'd rather find a commercial solution and be done with it. Any help will be greatly appreciated."
Looks like These guys have pretty close to your shopping list covered- they even have a phone with auto answer that has our friend, the standard 2.5mm universal headset port, which could be used for hooking up to the PA system.
SJW: a person who perceives an injustice, and while correcting it, commits a greater injustice.
Well, the visual alert part is pretty easy. Buy an ATA and a visual alert thingee for a regular analog line (I believe Radioshack and many online places sell them). The PA thing is harder, and I don't know of any devices that could easily do that.
Buy a two port ATA. If you can't find one, I can't help you.
Connect port one to a Viking Electronics Paging Controller. When you dial the ATA port one, it will answer. Connect it's output to the paging amp. Viking also makes other models, some with built in paging amp.
Connect port two to a Radio Shack Phone Flasher.
When you need to page, have * dial ATA port one.
When you want a call to flash the light, dial ATA port two along with the other phones. Remember you only want it to ring, not answer.
For paging you can also use a hacked up Grandstream phone, I have heard good results with these.
Or use the server's sound card.
Hope that helps!
--IronHelix
What I used to do for my own PA system is use the sound card in the old PC I had running Asterisk.
;;intercom
Use chan_oss or chan_alsa, and the Asterisk box takes care of the automatic picking up. It works great.
Grab a spare PC, install asterisk, do a IAX channel to it and it think you'll find it better, have more control.
The line in my asterisk setup was :
exten => 310,1,Dial(Console/dsp,10,A(tone11))
This dialed the Console, or sound card, then played a tone right before the channel went live, as a warning tone.
There's tons of applications for this. I used to have a program that somebody made that would say the incoming callers
Caller ID name and number over the intercom as the phones rang. Plus, you could dial in mp3 requests and i'd use mpg123.
Good stuff. I'd recommend going this route. you don't need a huge, fast new PC, I did it with a P2 450, and it sounded great.
--- Kicking the Cheat since late 2002
Is your Asterisk server a PC of some sort? Or is there another PC (or laptop) that you could use for patching to the PA system? I would think you could get an SIP software phone package, and hook the pc sound card output to the PA system. Configure the SIP soft-phone to auto-answer (I think that one of the many SIP software packages out there would have an auto-answer feature), and you have your patch.
The flashing-light thing sounds a bit trickier, but I bet you do something like the following: get an SIP-to-analog converter. The kind that you plug an analog phone into a socket on the converter, and plug the converter into an ethernet jack. Then, find an old telephone that actually had a physical bell inside it, with electric wires to drive the motor to ring the bells. Cut the leads that go to the motor for the bell, and use the current coming on those wires to light up a light, maybe? Or at least, use the current as a switching mechanism to turn on a circuit that lights up the lights.
If you don't feel inclined to do hardware hacking, someone *probably* sells an SIP device that will create a visual alert when the device is signalled for a phone call.
Most ATA devices do not have proper disconnection supervision on incoming calls. (google for CPC Duration on Sipura ATAs).
This will cause problems as the ATA will not hang up the Viking controller when the call ends.
My recommendation would be to swap out the ATA for a Sangoma or Digium FXS card and use a Bogen TAM-B or somesuch paging controller.
The FXS card will do the right thing and hang up when the call is ended.
Another option is a Grandstream GXP-2000 which has a 1/8 stereo jack in the side.
Rumor has it that the latest GXP-2000 firmware does the right thing on hangup but I haven't tested that. The old firmware played a beeping busy tone endlessly until you hit the speakerphone button to hangup.