Busying a telephone line

[terryk]

We have just moved offices.

At our old office we had BT installed switches which allowed us to busy out some of our incoming lines on days when there limited staff in the office so callers who could not be answered got the engaged tone rather than hearing the phone ringing off the hook.

Apparently BT no longer provide this service - at least not if you believe the three different sales people I have spoken to.

Obviously we can plug a phone into the socket of a line we wish to busy and leave it off the hook - but then we get the louder and louder tones and finally the howling which is not very elegant.

Does anyone know of a module fitted to a BT plug which would achieve the same effect as the old switch did - or does anyone know how we could make such a module up. Presumabley we need to take pins 2 and 5 - but do we put a resistor between them or what?

Any ideas gratefully accepted.

 

[RF Lighting]

What about a phone with an RJ11 connector in the bottom of the handset? Simply unplug the handset to stop the off the hook warning tone

 

[terryk]

What about a phone with an RJ11 connector in the bottom of the handset? Simply unplug the handset to stop the off the hook warning tone

That's an idea - which I hadn't thought of. As a result I didn't put this in the original post so as not to over complicate it - but we have six lines which have sockets on the incomer before going into a PBX. We sometimes busy out up to three - so it would be nice if we could find a "mini" solution so we don't clutter the place up with off the hook phones! Wish I had looked inside the BT supplied switch at the old office before we moved!

 

[big-all]

What about a phone with an RJ11 connector in the bottom of the handset? Simply unplug the handset to stop the off the hook warning tone

i had a phone where the cable unclipped to the hand set and when it did it bypassed the hangup button

i other words removing the handset was like hanging up!!!!

 

[peterpumpkin]

BT used to provide a busying out service,they had a sliding switch, that put a resistive loop across the last line, and this operated a relay in the exchange that busied out all/some the others.
All you need to do is put a short cct across lines you don't need to ring
ie. tmls 2+5 , this might show up as a fault in the exchange, and BT might disconnect you!
depending on your system, there may be a programmable facility to busy out lines.
What system is it?
pp.

 

[terryk]

Yeah that was the sliding switch we had. If possible I'd like to recreate that using a BT plug to bare ends and some soldering and then enclose it in a small case - but I don't know the resistance required etc. I agree just shorting 2 and 5 might not be the best plan!

We have a revelation system - problem I have got is that even if we can program it, I don't want everyone fiddling with it or they'll be taking the bars for 090 and directory enquiries off!

 

[peterpumpkin]

Sorry, don't know the the revelation, too new for me!
a Normal telephone is usually less than 1000 ohms, so a resitive loop of less than that will simulate a telephone loop,
BT might still see this a fault though! but I don't think they have the resource to be bothered anymore?
pp.

 

[terryk]

So if I assume phone is nominally 75 volts and go for 750 ohm looks like that might do the trick.

 

[JOHNBOY42]

Simple solution, just buy the extension leads from £1 shop ,chop the leads off and bare all the wires and solder together ,then plug into the sockets you require busying out , and anybody dialling into them lines will get a engaged tone...ie if you have only 3 staff in you could put this into lines 4,5 and 6 .....a fault wont be raised unless you ring bt to say you have a problem

 

[bernardgreen]

The busying resistor as to be one that draws about 40 mA from the line.

Telephones are designed to adjust their internal "resistance" to draw the optimum current from the line by using a constant current circuit.

A simple resistor will need to be chosen by trial and error as the length of the telephone line ( it's resistance ) will affect the value required.

 

[peterpumpkin]

Hi, Spoke to revelation man to-day, his solution would be to program the lines onto individual buttons on a system phone, and seize each line in turn, and put them into hold.leaving the receiver off,otherwise the lines will revert. Then when you want to release them just reverse the procedure.
pp

 

[plugwash]

shoving 1K or so accross the line should work fine. I can't imainge older phones did anything as posh as drawing a constant current.

 

[Softus]

All you need to do is put a short cct across lines you don't need to ring

Of all the f***ing stupid ideas I've read, this takes the biscuit.

 

[bernardgreen]

shoving 1K or so accross the line should work fine. I can't imainge older phones did anything as posh as drawing a constant current.

quoted from http://web.ukonline.co.uk/freshwater/t706.htm

Unlike the 200 and 300 types the 706 was at last a truly modern looking telephone. It had smooth curves and ergonomic design, was lightweight, colourful, and versatile. The same telephone could be used for many applications by changing the removable dial surround and also had a blanking plate covering a hole which could be removed to allow different switches to be fitted. Inside it contained the latest circuit technology including a plug-in current regulator and option of printed circuit board wiring (see below).

.......On earlier models the resistance lamp on the regulator board had just a clear glass finish - unfortunately some users were perturbed by the glowing coming from within their instruments if they were used in the dark (especially red models!) and later releases have the resistance lamp painted black.

A similar resistance lamp regulator was used in other types of phones before semi-conductor circuitry took over.

 

[MarkBarl]

Anyone heard of Voicemail?