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Old 11th Feb 2019, 12:21 pm   #1
boombox
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Default BT Inspiration (+ Versatility etc) PA Connection?

Hallo

I wonder if anyone has any hints or tips about BT PBXs and connecting them to PA systems? The manuals always just refer opaquely to connecting them to a PA system but does that mean I need to spend 1K on a "PA system" or could I just connect up to a 15 digital T Amp and a pair of speakers?

Thank you!
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Old 11th Feb 2019, 5:43 pm   #2
OscarFoxtrot
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Default Re: BT Inspiration (+ Versatility etc) PA Connection?

They are usually a standard 600 ohm line level mono output.

I can't see in the Insiration manuals where you actually connect the PA output. There's a reference to a BT80A, and turning paging on in programming, but no cable actually shown. Does it use a spare extension port?
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Old 11th Feb 2019, 6:17 pm   #3
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Default Re: BT Inspiration (+ Versatility etc) PA Connection?

Hmmm - found a PDF here - can't find ANY reference to the device they mention online, sadly!
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Old 11th Feb 2019, 7:52 pm   #4
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Default Re: BT Inspiration (+ Versatility etc) PA Connection?

Aha. That's a very different kettle of fish.

It needs something that will present as a telephone interface. Simplest to make is probably a telephone recording circuit like these.

http://www.epanorama.net/documents/t...elerecord.html

and to make it always off-hook with a 600 ohm resistor in parallel (or one slightly more so the combined impedance across the line is 600 phm).

You might also be able to adapt an old answering machine that answers the line, plays a 'ding dong' as the OGM, then you can speak. You'd have to wipe the tape/memory occasionally as it filled up.

The official version would be an interface like this
https://www.baldwinboxall.co.uk/bt-interfaces/

They do pop up on ebay varying from cheap to most spendy. BT5 maybe 150 used/unsold or about 400-450 new.
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Old 12th Feb 2019, 5:30 pm   #5
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Default Re: BT Inspiration (+ Versatility etc) PA Connection?

We use a unit made by Baldwin Boxall, which gives an audio output of 0dbm into 600 Ohms (775mV) and has a digital storage device to give a delay. This is necessary to prevent howl-round. Various open collector switches are available too.

It may be possible to make one using bucket-brigade technology but will be disconcerting if the delay isn't long enough, ie a delayed message is broadcast when you are still speaking!

Ours is effectively an analogue telephone extension: dial a 'PA' number, rings three times then speak and hang up. The message is then broadcast.
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Old 12th Feb 2019, 5:52 pm   #6
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Default Re: BT Inspiration (+ Versatility etc) PA Connection?

Quote:
Originally Posted by russell_w_b View Post
We use a unit made by Baldwin Boxall
Thanks Russell - something like this? Would that on its own be enough extra hardware to make "the magic come alive" ? ;-)
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Old 12th Feb 2019, 8:48 pm   #7
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Default Re: BT Inspiration (+ Versatility etc) PA Connection?

That's a PA amplifier.

You still need an interface between the extension phone line and the PA system.

It might be easier to swap systems to something like a Panasonic KX-TA which has an audio line level paging output or put one on a spare exchange line so you can do [line]330 to page out through the Panny.
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Old 12th Feb 2019, 10:05 pm   #8
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Default Re: BT Inspiration (+ Versatility etc) PA Connection?

"Valcom" was the PA adapter I used to install. It just connected to a spare POTS extension port.

The type we used had no delay.
In one large factory feedback was a serious problem, but I solved it by identifying the phones that were likely to be used to make announcements and desensatised the microphone with a series resistor.

This also improved normal calls because the factory was very noisy and you needed to shout anyway.
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Old 13th Feb 2019, 11:06 pm   #9
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Default Re: BT Inspiration (+ Versatility etc) PA Connection?

Hi, I'm not sure about the Versatitlity however I have had a look a the inspiration manuals here and it appears that it is possible to program an extension position as a PA port.

The Inspiration is very similar to the Revelation and I have configured my Revelation so that one of the extension ports acts as a PA output when dialled - the caveat is that you will need something like this connected to the nescassary extension port as the amplifier.

I'm sure I tried with a standard loudspeaking telephone left off hook on my Revelation PA extension port, I can't recall if the line timed out after so long in that case though.

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Old 14th Feb 2019, 12:56 am   #10
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Default Re: BT Inspiration (+ Versatility etc) PA Connection?

Quote:
Originally Posted by OscarFoxtrot View Post
That's a PA amplifier.

You still need an interface between the extension phone line and the PA system.

It might be easier to swap systems to something like a Panasonic KX-TA which has an audio line level paging output or put one on a spare exchange line so you can do [line]330 to page out through the Panny.
KXTA wera a dwadle to set up a PA system on. Hardest job was making up a connect cable. Second hardest job was getting customer trained to use it.
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Old 14th Feb 2019, 5:02 pm   #11
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Default Re: BT Inspiration (+ Versatility etc) PA Connection?

Don't suppose anyone has any old kit lying around we could buy? Loathe to throw 100+ at new kit on eBay it as it's more a convenience/fun thing rather than anything mission critical.
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