Is anyone aware of a device that will convert a US POTS phone line to "standard" audio inputs and outputs?

I'm trying to connect a video conferencing system to our phone system so that people who are remote can dial into a phone number and listen and speak with the other conference attendees. The video conferencing system has a 1/8" phono (TRS) jack audio input and RCA audio outputs. But any device that gets a phone line converted to any standard audio format would work.

The device would have to have some smarts, most likely, so that it would only pick up the line when someone else has first, or activated with a switch, or something. I suppose I might actually be able to do this with a computer with a voice-enabled modem. But a standalone device would be cool.

In broadcasting they're usually referred to TBU's (Tele Balance Units) or Hybrid's. These units are usually very expensive but have auto-answer, echo cancellation, auto adjust for side-tone and the like.

If I was going to do it on the cheap I'd probably take an ordinary phone and hack the handset off. Then I'd grab a couple of isolating transformers and use them to bridge the phone to the conference system.

If you don't fancy hacking a phone apart, then a quick google turned up the Excalibur HC-1 (scroll down a bit), only $88. It doesn't auto answer though.

Yeah, the circuit to put in an isolating transformer is quite simple, I remember building one many years ago with something like two radio shack parts. I think I was trying to build a cheap speakerphone or something. I don't remember exactly what I did, though.

Turns out that, although the isolating transformer is simple, tricks like echo cancellation and prevention of feedback is very difficult.

Ooh, so close. That device deals with the handset line, not the POTS line. Basically a hands-free adapter without a headset. And, of course, the phone in there has no handset.

Those are a bit harder to find since they also must include all of the electronics that a telephone contains. But yeah I understand what you're looking for.

It strikes me that the sort of thing that you need is *almost* an answering machine. All of the bits are there (including microphone input), it's just a question of how/when each bit of audio signal gets routed.

I'm surprised your video conferencing system doesn't already include this kind of thing. Sounds like the video conferencing system is (deep inside) just a PC, and all it would need was a voicemodem card and some software jiggering.

Something like this? Wrong type of audio interface tho...

It's a Polycom VSX 7000. Their solution is a specific Polycom speakerphone. We already have a Polycom speakerphone, but not the right one. The right one is like $800. I was just trying to avoid that.

We've got a Polycom here and the main unit is the same between all interfaces. The big adapter block that lives under the desk is the only part that changes. They won't sell you that bit?

Hm. They do look virtually identical. I'll see if there is an upgrade path.

There's probably a firmware difference, too.

Ah. Those people know what they're doing in terms of conference phone audio. That gear is the *business*. I've used them in more than one company I've worked for, and they impress me every time.

Their video conferencing system, though, is remarkably abstruse. The UI is awful and the documentation nonexistent. Once you figure out which of a million different options to tweak, though, it works just fine.

They really know what they're doing in terms of pricing. Bitt's system probably cost between 8k to 12k, and then they'll charge $$$ for every last accessory, including my favorite, the telephone cable with RJ-11 that have uncentered tabs for the microphone.

We've had 7000e at work for about 6 months, and it's been used once so far. At a five year life span, if we maintain our current usage, it'll be 1k per use easy, not including the support time to set it up and figure out how to work it every six months..


You've got my sympathies dealing with the lack of documentation, the interface is easy enough for the end user but impossible to figure out how to set up, obviously they'd like you to pay 2k for installation each time you'd like to move the system.

Matthew

I didn't purchase this system; it was provided by corporate, though I'm sure that you're probably right about the cost, and you're definitely right about the accessories. However, you forget to mention that it's useless without at least one other equivalent system. So double or triple that.

Ours does actually get used fairly frequently, though. Probably several times a week on average. I don't know that it's worth it; I'm not sure what's wrong with the phones.

Have you tried it with just putting the voice caller on speakerphone in the same room where the videoconferencing stuff is? I'm pretty sure we used to do conferences like that without any actual connection between speakerphone and videoconference system. (It got a bit crappy when there were voice callers speakerphoned in at both ends of the videoconference, though.)

This was with all Polycom gear.

Peter

Yeah. My manager claims it doesn't work all that well. It does work, though.