Ferdinand Babas
2011-Nov-30 21:20 UTC
[asterisk-users] Walkie talkie to sip phone interface
Hi All, I've been trying to find a solution that would allow our sip phones to communication with walkie talkies. Our setup is that we have sip phones setup in 2 locations, headquarters and dome. We can communication from headquarters and dome through sip phones, but within the dome we have technicians that use walkie talkies to communicate as they go about their work. Our hope is to allow 2 way communications from our sip phones at headquarters (or within the dome) with our technicians using their walkie talkies as they are working throughout the dome. Not sure if this is possible but I would appreciate any suggestions. Thanks, Ferdinand
On Wed, Nov 30, 2011 at 6:20 PM, Ferdinand Babas <babas at cfht.hawaii.edu> wrote:> Hi All, > > I've been trying to find a solution that would allow our sip phones to > communication with walkie talkies. ?Our setup is that we have sip phones > setup in 2 locations, headquarters and dome. ?We can communication from > headquarters and dome through sip phones, but within the dome we have > technicians that use walkie talkies to communicate as they go about their > work. ?Our hope is to allow 2 way communications from our sip phones at > headquarters (or within the dome) with our technicians using their walkie > talkies as they are working throughout the dome. ?Not sure if this is > possible but I would appreciate any suggestions. > > Thanks, > > FerdinandYes there are interfaces for POTS, SIP, H323 and others. People could help if they knew what type of signaling or vendor you are using. A google search gave me this. http://www.motorola.com/web/Business/Products/Two-way%20Radio%20Infrastructure/Gateways/MOTOBRIDGE%20Interoperable%20IP%20Solution/_Documents/MotoBridgeSS_Final.pdf -- ~ Andrew "lathama" Latham lathama at gmail.com http://lathama.net ~
> I've been trying to find a solution that would allow our sip phones to > communication with walkie talkies. Our setup is that we have sip phones > setup in 2 locations, headquarters and dome. We can communication from > headquarters and dome through sip phones, but within the dome we have > technicians that use walkie talkies to communicate as they go about > their work. Our hope is to allow 2 way communications from our sip > phones at headquarters (or within the dome) with our technicians using > their walkie talkies as they are working throughout the dome. Not sure > if this is possible but I would appreciate any suggestions.It's definitely possible. How practical it is, remains to be seen and is probably a "how well do the details work out?" issue. The simplest approach is probably this: you'll need a walkie talkie "base station" which will serve as the transmit/receive point for the dome. The most straightforward would be to use one of the actual walkie talkie radios, with a well-filtered DC power supply in place of a battery pack. You would need to hook up the W/T's "speaker out" and "mic in", and perhaps the "push to talk" line, to suitable audio and control I/Os on some sort of Asterisk end-point. The least expensive way would probably be to use the Asterisk server itself (or some PC running a soft-phone client), and use the PC/server's sound card jacks. You would need some sort of level-adjusting (padding) system for the signal being fed into the walkie talkie's "mic" input (these generally require much less voltage than a sound card's line-level output), and it would probably be a good idea to have an audio isolation transformer in each audio path to prevent ground loops and hum and RF pickup. You'd need some way of keying the radio's push-to-talk when someone on the phone starts to speak, and then release PTT when the voice stops. Some walkie talkies have a VOX (voice-operated switch) which will do the job. Others do not, and you would need a separate VOX circuit (not difficult). One possible hardware device which might save you trouble is the Tigertronics SignaLink USB - it's primarily designed for and sold to amateur-radio operators but has multiple uses. It consists of a USB "sound card", isolation transformers, an adjustable VOX/PTT circuit, and a very flexible radio-interconnect-cable system which you could adapt to the speaker/mic needs of your walkie talkie. You'd simply plug it into the server's USB jack, and it would become a secondary audio interface. On the Asterisk side, you'd want to use the ALSA channel driver, and create an inbound extension which would simply "dial" the ALSA channel. Or, you might decide to use one of the various Asterisk bridging/conference applications, and have the ALSA walkie-talkie channel be perpetually signed into a conference bridge which one or more other users could phone into. You'll need to select and implement a suitable security policy, to control who can access your dome audio link, and decide whether someone in the dome can use a walkie talkie with DTMF capability to dial calls or otherwise control the Asterisk system via radio. Finally, you need to make sure that all of this is legal in your particular jurisdiction. Here in the U.S., there are quite a few personal and mobile-radio services for which it is *not* legal to create a connection to the wired telephony system. This is probably something you should determine first, rather than at the end.