Cross Compatibility of Comms Systems.

[James Remo]

I've come across a comms beltpack made by "Mac Communications" It has a 3 pin male XLR and a 4 pin female XLR on the bottom, and controls for two circuits on the top, with one call button. Has anyone come across one before? The only thing I can find on google is someone on studiospares.com inquiring about them, with no replies. I thought they might be connected to Mac Sound in Manchester, possibly an in-house construction? Does anyone have a friendly contact who works there, or who has worked there (as this system isn't listed on their current rate card I don't think they will still stock them) who might be able to provide any insight?

Cheers,

James

[Hilary Watts]

I've come across a comms beltpack made by "Mac Communications" It has a 3 pin male XLR and a 4 pin female XLR on the bottom, and controls for two circuits on the top, with one call button. Has anyone come across one before? The only thing I can find on google is someone on studiospares.com inquiring about them, with no replies. I thought they might be connected to Mac Sound in Manchester, possibly an in-house construction? Does anyone have a friendly contact who works there, or who has worked there (as this system isn't listed on their current rate card I don't think they will still stock them) who might be able to provide any insight?

Cheers,

James

 

...bump!

 

It doesn't look as if this post has achieved any response but I'm hopeful that someone can help as I have been handed two beltpacks made by 'Mac Communications Manchester' which I've been told need repairing. I've connected them to a Tecpro power supply since they have a 3 pin XLR connector with supply, ground and signal lines but at first sight neither seem to work at all. However if listening carefully a test tone can just be heard in the headphones when it is fed into the system and is affected as you would expect by the setting of by the phones volume control, but even at maximum the output is almost inaudible. In addition two LEDs (one connected to the 'push to talk' button and the other, presumably, a 'call' indicator) glow very faintly. The voltage across the LEDs when lit appears to be 1.3v.

 

I'm beginning to wonder whether they are intended for a higher voltage supply than than the 24v provided by the TecPro unit but I don't have access to a variable DC supply and in any case I don't want to risk destroying the units if my theory is not correct!

 

I have tried to trace Mac Comunications but have drawn a blank. A company of that name was wound up last year but the registered office had an address in Middlesbrough and I am not sure if it was the same organisation. I suspect the units I have are at least 10 to 15 years old so the manufacturer could have ceased trading years ago. There is no information on the PCB other than the number CM84S. I can't get any information from the theatre to whom the units belong as the person that would have known has now died (which is why I have been asked to have a look at them in the first place!).

 

 

Does anyone have any information that might help ?

 

Hilary

[Seano]

I have tried to trace Mac Comunications but have drawn a blank.

 

There is a MAC Sound in Manchester, and has been for many years now, perhaps they could shed some light.

[Hilary Watts]

There is a MAC Sound in Manchester, and has been for many years now, perhaps they could shed some light.

 

Thanks - I've emailed them.

[Dmills]

IIRC RTS had a 2 circuits over 3 wires system that was incompatible with the common techpro/Clearcom. I seem to recall that they called the wiring system TW or something of the sort and that it ran two unbalanced audio circuits over pin 2 & 3 with power fed onto both lines via a gyrator to isolate the audio.

 

http://www.epanorama.net/links/intercom.html has some stuff if this is RTS TW standard (see section about 2/3rds of the way down).

 

HTH.

 

Regards, Dan.

[Hilary Watts]

Dan, thank you for the helpful information. What you say is confirmed by an email which I have received from David Houghton at Mac Sound who says:

 

"We are the MAC you are seeking but unfortunately I'm not sure I can

help you very much. The comms were manufactured many moons ago by PB theatre systems

with our name on the front. They run on 24 volts but are not compatible with Tecpro

/Stonewood etc which is probably one of the main reasons for their demise. We never had the

circuit diagrams although I don't think there are any mystery components in them, we no longer

have any spares or any means of providing back up for them.

 

Sorry I cannot be of any more help."

 

It's now clear why the units won't work with a Tecpro PSU - it seems likely they were left over from a previous system which was replaced with the current Tecpro set-up. Of course, if there are enough bits and pieces lying around then I may be able to get them working as a self-contained system...time to use Dan's link and research the RTS TW standard methinks!

 

Hilary