DIY Comms

[cjlowe]

Hi there.

Does anyone know of a way to build a DIY Clear-Com-compatible comms box?

The phone system seems like a great idea and I'm going to experiment with it - I'm just concerned about the volume levels. Sounds like it will be almost unusable in a live environment without some serious work (of course I'll be adding momentary/constant PTT switches).

We just haven't got the budget for Clear-Com at the moment, so any help with a DIY solution would be greatly appreciated.

As an aside - given both the phone and the Clear-Com system are just a party line + power, I can't help but wonder if they're compatible with a little pin mangling. Anyone know about this?

[karlp]

If you cant swing a clearcom, why not use Production Intercom?

Their econocom packages http://www.beltpack.com/body_econo.html may be just what you need. Call up Northern Sound and Light and ask for the pricing, you can generally get a fully 4 pack system with a PS for not much more than a single belt-pack and headset from CC. Add-ons are inexpensive as well.

Hope this helps

Karl P

[waynehoskins]

The circuit is pretty simple; the hard part is the box. The intercom bus is simply unbalanced line level (-ish) audio.

Ten years ago my dad designed a Clear-Com compatible system based on, but not a duplication of, their published schematic. He used one quad op-amp for everything, and of course Rs and Cs. The parts cost for the circuit itself is very low, especially if you're not having a short run of boards made.

That said, Tech Projects (Production Intercom) make good stuff. Rock solid construction, and like I said, the circuit is so stinking simple. And they're completely CC-compatible.

If you want a copy of our schematic, I have a copy somewhere I can email you or post or whatever. If you have a board maker, somewhere we have the board artwork (it fit on a 2x2 double-sided board; we made a run of 9 of them back then).

[sempei13]

I'd love the schematic. I do know that there's a pinout for both a clearcom headset (four pin xlr) and a trs from a standard telephone headset on pinouts.ru. It looks like the second uses a shared ground, so assuming resistance is the same, it looks like making one from the other would be simple. I'm planning on taking an older telephone heaset and making a clear-com version so that I can replace the one in the video booth that hurts my head.

Paul

[cjlowe]

I would LOVE the schematic - please upload it here so we may all bask in its glory... my plan at the moment is to buy/build several wired Clear-Com-compatible packs, then "bridge" the Clear-Com bus with a "Phone-Com"(R)(TM) network to give those who need them wireless comms (via DECT phones with headset jacks).

Sound good to you? Seems like a good idea to me. 

[waynehoskins]

I'll see if I can dig it up tomorrow. I've got it on one of the computers at the office .. you know how that goes .. dot matrix printout from Orcad those many years ago, scanned in later, knocking around somewhere. I think I can get my hands on it without much trouble.

It's a simple design: a TL084, two transistors for the call circuit, a handful of common value resistors and capacitors. Parts cost: dirt cheap.

(For what it's worth, the TL084 is a Texas Instruments quad op amp, JFET inputs I think .. if it's not readily available in AU land, it should sub easily enough with somebody else's).

[cjlowe]

Originally Posted by waynehoskins

TL084

Jaycar Cat.# ZL3084, $2 each ($1.80ea for orders >10).

[cjlowe]

Any luck finding it, Wayne?

[tedanderson]

One thing that I suggested for a client of mine is to use a decent high quality "whole house" FM transmitter and then give everyone a standard set of headphones with a pocket sized FM radio. This would only facilitate one-way communication but it would be effective. Everyone could control their own volume and it was less than $300 to get it up and going.

[waynehoskins]

Haven't found it just yet .. hopefully soon.

I haven't found just which computer it's on, but I have found a few that it's not on.

[tedanderson]

It's always in the last place that you look.

[Chris Everett]

http://www.rcrowley.com/ComClone/default.htm