telephone/audio intefaces?

[avdavesound]

Hi, I came across an install today where they where using the phone in reception to page, all you have to do is diall ext 42. know how this is done? also had a look at the back of the mixer/amp and there was a jack plug, with resistors or something wired inline (bodge job) but it works. is there a special unit that can do this?

[peternewman]

You want something called a TBU or Telephone Balance Unit. For example the first relevant hit on Google (here). I don't quite understand the amp and jack comments.

[Jivemaster]

Certainly many radio broadcast sound desks of the manual fader type have channel modules for phone lines -the module holds a telecom line and allows level control of the in and out signal

 

chat to Alice Broadcast or Partridge (Benfleet) If he is still there.

[avdavesound]

I don't quite understand the amp and jack comments.

theres a jack plug on the end of a cat 5 with something wired inline like a resistor. jack plug is plugged into the mic input on the mixer/amp.

[Jivemaster]

Most phone lines have 50v AC and 50v DC for various purposes so there is probably an attenuator and an isolator -I can't see 50v doing much good to a mic level input.

[bruce]

The jack plug and resistors thing sound like a simple attenuator - the output coming from the phone interface may be too "hot"

for a mic input.

 

For this sort of applictaion, you probably don't need a full TBU, as there's no return path, no need to put callers on "hold" etc. You just need a "telephone paging interface". Some PABXs will have one of these as standard, with others, it's a small box of tricks which connects in just like a normal extension.

[dbuckley]

Three ways to do this "properly"

 

1) The PABX may have integrated paging support, requiring nothing more than an audio cable wetween the "paging out" jack and the line input of a PA amp.

 

2) The PA amp may have a paging input, designed to connect directly to a phone line; some models of amps from Toa and Inter-M do this.

 

3) You need a box in the middle. Viking PI-1, google for suppliers. Don't be tempted to try the RDL ST-TC1, it isn't a paging interface.

[dosxuk]

Biamp Audia DSP units can have a telephone interface card fitted, which could be suitable for this purpose.

 

Look at the "TI-2 Dual-Channel Telephone Interface Cards" on this page: http://www.biamp.com/audiaflex.php

[avdavesound]

now the tricky bit, I need to send that telephone page to 3 more locations. they have a seperate sound system in each location. distances range from 500m to 800m. what would be the best way to do it? split it at the telephone junction/patch box and use a telephone paging interface at each location?

.

[dbuckley]

No, absolutely not, use just one paging interface and split the audio, using a DA with output transformers would be my recommendation, so a press splitter box is probably the easiest thing to use. If you have phone wire available (CW1308, a/k/a cat3) or Cat5 you can send balanced line audio over that wiring, so no extra cables to run

 

If you use three paging interfaces you could get into race conditions where one answers and the other two then dont bother...

[avdavesound]

No, absolutely not, use just one paging interface and split the audio, using a DA with output transformers would be my recommendation, so a press splitter box is probably the easiest thing to use. If you have phone wire available (CW1308, a/k/a cat3) or Cat5 you can send balanced line audio over that wiring, so no extra cables to run :)

 

If you use three paging interfaces you could get into race conditions where one answers and the other two then dont bother...

Thanks. Its all cat 5 so will I just wire an XLR each end of the cat 5 or will I need some sort of baluns

[bruce]

If it's a balanced input and output, an XLR on the cat5 should be fine. Just make sure you pick up 2 cores from the same pair.

 

If unbalanced - well, there's a chance that you might get away with it, but a balun would be the proper way to do it.

 

As a matter of interest, what was the cat5 installed for? if it is really 800m, then it's unlikely to be a data installation.

[avdavesound]

If it's a balanced input and output, an XLR on the cat5 should be fine. Just make sure you pick up 2 cores from the same pair.

 

If unbalanced - well, there's a chance that you might get away with it, but a balun would be the proper way to do it.

 

As a matter of interest, what was the cat5 installed for? if it is really 800m, then it's unlikely to be a data installation.

 

its not installed yet but I spec'd cat 5e to cover the few possibility's. there's 3 new warehouses being built and I spec'd a cat 5 to run from the main warehouse coms/amp room to the 3 new warehouses. I'll have a 100v mixer/amp in each warehouse to cover the area. so all I need to do is get the page to each location.

[dbuckley]

You'll recall I did say transformer isolated DA, wont you, as the earth potential in each building will be different, and joining them together using Cat5 could be bad for the Cat5!!!!! Think heating, melting etc. I saw this coming, which is why the recommendation :)

 

So just use pin 2 and pin 3 to a cat5 pair at each end, and leave pin 1 unconnected, and all will be well.

 

If you are unbalanced line in, then you will need to send balanced audio, but use a balun at the receiving end.

[avdavesound]

You'll recall I did say transformer isolated DA, wont you, as the earth potential in each building will be different, and joining them together using Cat5 could be bad for the Cat5!!!!! Think heating, melting etc. I saw this coming, which is why the recommendation :)

something like this linky?

 

Thanks for all your hep.