# Clearcom/Telex Systems Integration



## MaxS (Jul 2, 2010)

I'm prepping for a show later this month, and we're renting out a Telex BTR-200 system to expand our current Clearcom wired IC. I was told that it wasn't compatible, so I sent the following email to our TD as a potential fix:

> Given the model of the Telex basestation, it may be possible to wire an interface between the systems. The pinout for Clearcom 3XLR is as follows:
> 1 = Ground/Shield/Common
> 2 = +24-30 VDC
> 3 = Tx Signal (+5-10VDC for call)
> ...



After doing some more digging, however, I found that the manual describes how to use internal DIP switches to configure the unit for Clearcom interoperability on pages 20-21. This makes my previous plan irrelevant for this particular application.
http://www.swaindigital.com/ebay/BTR-200 TR-200 Operating Instructions.pdf


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## museav (Jul 2, 2010)

Max, was this something where others might potentially run into the same problem and benefit by knowing how you solved it?


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## MaxS (Jul 2, 2010)

Sure, it might. Sorry, it was late and I had just finished up striking a show. I had a "duh" moment when I finally found the manual for the unit, however the original solution that I had come up with may still be used by someone if it works. Telex also makes an interface unit of their own, the CCB-1.


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## WooferHound (Jul 2, 2010)

MaxS said . . . - Quote -
Given the model of the Telex basestation, it may be possible to wire an interface between the systems. The pinout for Clearcom 3XLR is as follows:
1 = Ground/Shield/Common
2 = +24-30 VDC
3 = Tx Signal (+5-10VDC for call)

The original, legacy Telex series pinout is as follows:
1 = Ground/Shield/Common
2 = - Signal Polarity
3 = + Signal Polarity
- End quote -

The Clearcom pinout is accurate, but your Telex pinout does not include the power arrangement that powers the beltpack. It works very much like Phantom power where the Positive voltage appears on both of the 2 signal wires, and the Negative voltage appears on the shield/drain. Because of this it is not possible to make an adapter to connect the 2 different systems together.


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## Chris15 (Jul 4, 2010)

WooferHound said:


> The Clearcom pinout is accurate, but your Telex pinout does not include the power arrangement that powers the beltpack. It works very much like Phantom power where the Positive voltage appears on both of the 2 signal wires, and the Negative voltage appears on the shield/drain. Because of this it is not possible to make an adapter to connect the 2 different systems together.



Um... When was the last time a transformer cared about a common mode voltage, say like phantom power?


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## WooferHound (Jul 4, 2010)

A transformer will not pass a DC voltage, and it doesen't care if one side of a DC voltage is presented to both sides of any of the windings, therefore a transformer will not pass the voltage that an intercom system needs to operate, Therefore it is not possable to make an adapter to go between a Telix and a Clearcom system.


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## MaxS (Jul 4, 2010)

WooferHound said:


> A transformer will not pass a DC voltage, and it doesen't care if one side of a DC voltage is presented to both sides of any of the windings, therefore a transformer will not pass the voltage that an intercom system needs to operate, Therefore it is not possable to make an adapter to go between a Telix and a Clearcom system.



You forget that the Telex leg contains its own basestation, a self-powered wireless transceiver. Therefore it is already supplying its own power to its side of the transformer. The transformer won't pass along the phantom-style DC current from the signal wires in the Telex leg, which is actually ideal. The DC supply from either side has no means of reaching the other, allowing for a simpler design that only deals with the actual audio signals. The only limitation of what I've laid out is that calling will be disabled from both sides, between the capacitor/transformer on the Clearcom side, and the fact that a 20KHz tone is used on the Telex signal wire, as opposed to a voltage bump.


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## Chris15 (Jul 6, 2010)

MaxS said:


> You forget that the Telex leg contains its own basestation, a self-powered wireless transceiver. Therefore it is already supplying its own power to its side of the transformer. The transformer won't pass along the phantom-style DC current from the signal wires in the Telex leg, which is actually ideal. The DC supply from either side has no means of reaching the other, allowing for a simpler design that only deals with the actual audio signals. The only limitation of what I've laid out is that calling will be disabled from both sides, between the capacitor/transformer on the Clearcom side, and the fact that a 20KHz tone is used on the Telex signal wire, as opposed to a voltage bump.


 
The wireless base doesn't probably have a PSU in it, but it doesn't need one either.
The call should still work on each side of the ring, but it just won't traverse the connection between the two. If you find that the clearcom side is not behaving quite as it used to, throw a capacitor in series with the transformer and that ought to sort the problem out...


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