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uk.telecom.voip (UK VOIP) (uk.telecom.voip) Discussion of topics relevant to packet based voice technologies including Voice over IP (VoIP), Fax over IP (FoIP), Voice over Frame Relay (VoFR), Voice over Broadband (VoB) and Voice on the Net (VoN) as well as service providers, hardware and software for use with these technologies. Advertising is not allowed.

Payphone 500 / 600 handset



 
 
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  #1  
Old July 27th 18, 02:49 PM posted to uk.telecom.voip
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Default Payphone 500 / 600 handset

Hi

I have some BT handsets with the armoured cord as used on Payphone 500 / 600 (the 700 style handsets, not the flat angular ones)

They are of course riveted shut preventing internal examination. They have 6 wire cords (red, grn, blu, whi, org, blk)

Are these standard 700 style inserts and on the standard colours red+grn for receiver, blue+white for xmtr? as I am having difficulties getting them working.

On one of them red+grn makes the mouthpiece work as a receiver.

I want to repurpose them for an application requiring 700 type circuitry.

Thanks

Owain

(only on google groups, so can't read or post to uk.telecom)
  #3  
Old July 27th 18, 07:46 PM posted to uk.telecom.voip
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Default Payphone 500 / 600 handset

On Friday, 27 July 2018 14:18:51 UTC+1, MissRiaElaine wrote:
I have some BT handsets with the armoured cord as used on Payphone 500 / 600 (the 700 style handsets, not the flat angular ones)
They are of course riveted shut preventing internal examination. They have 6 wire cords (red, grn, blu, whi, org, blk)

[Cross-posted to uk.telecom]


Thank you. I can't see or post there ATM.

My advice would be to use a small drill and *carefully* drill out the
rivets so you can open it up and have a look.


I have drilled out the mouthpiece rivet and can report:

* blu/whi are used for transmitter

* transmitter is a Receiver 4T in black rubber mouldings. Not enough space for the mouldings and a Transmitter 16, and presumably they wanted to reduce handling and wind noise. There is a purple plastic sheet to spit-proof the transmitter

* org/blk are joined together and sleeved in the transmitter compartment, presumably to provide a cut cord detection circuit

* red/grn go up the handset to the receiver. I haven't drilled open the receiver as the damage would be noticeable there, but it clicks nicely on a PP3 battery and I assume it's also a 4T.

*there appears no way of undoing the armoured cord entry and the wires are very reluctant to pull through any longer.

I was a bit surprised the mouthpiece was only riveted, and not glued shut as well, I don't think it would be possible to re-rivet it closed after drilling out, so the entire handset must have been treated as non-repairable.

Having now verified the handsets are all intact I can get to work on the circuit. I'm hoping that simply removing the resistor providing battery voltage to the carbon transmitter will do for starters ...

The circuit I'm building is here
https://www.vintage-radio.net/forum/...8&postcount=20
"741-field-telephone-system-intercom-PW1980.pdf"

Thanks again - was there anything else I should have seen in uk.telecom?

Owain

  #4  
Old August 7th 18, 08:56 PM posted to uk.telecom.voip
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Default Payphone 500 / 600 handset

On Friday, 27 July 2018 18:47:00 UTC+1, I wrote:
* red/grn go up the handset to the receiver. I haven't drilled open the
receiver as the damage would be noticeable there, but it clicks nicely
on a PP3 battery and I assume it's also a 4T.


Despite drilling out the receiver rivet, it refuses to open.

The receiver, I think, is not a plan 4T as it only clicks loudly one one polarity from a PP3, and very faintly on reverse polarity.

It gives unusably low volume connected to the circuit, which incidentally works lovely on 'standard' handsets (and gives quite astonishing volume into a 3
30 ohm 30 watt 100 volt line PA horn speaker)

Still hoping someone knows what's exactly inside these handsets

Owain


  #5  
Old August 15th 18, 09:57 PM posted to uk.telecom.voip
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Default Payphone 500 / 600 handset

On Tuesday, 7 August 2018 19:56:03 UTC+1, wrote:
The receiver, I think, is not a plain 4T as it only clicks loudly on one
polarity from a PP3, and very faintly on reverse polarity.


I can now report that
- wrapping doublesided sticky tape round the earcap provides sufficient grip to remove it.
- inside their is a Receiver Inset 2/3T and made by Hosiden-Besson (Code DAE). Splitting this open shows a small moving armature receiver (a normal 3T?) connected *in series* with a large coil round the outside for inductive coupling.

see bottom of
http://www.samhallas.co.uk/collectio...3_variants.htm

So I guess my question now is why won't a 2/3T work on a circuit where a 4T does? There are no transistors or anything else active in the 2/3T so it can't be needing a DC bias voltage.

Any ideas anyone? I'd really rather avoid drilling out all the receiver caps to change the inserts.

Owain
  #6  
Old August 15th 18, 10:57 PM posted to uk.telecom.voip
MissRiaElaine[_2_]
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Posts: 135
Default Payphone 500 / 600 handset

On 15/08/18 20:57, wrote:

see bottom of
http://www.samhallas.co.uk/collectio...3_variants.htm

Ah, good man, Sam. Not seen him for ages, we were on the committee of
the BARTG (British Amateur Radio Teleprinter Group) together many moons
ago :-)

--
Ria in Aberdeen

[Send address is invalid, use sipsoup at gmail dot com to reply direct]
 




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