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Old 25th May 2020, 11:08 am   #1
Sparks
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Default GPO Jack unit 1B and regulator 6B

Quick questions. Does this regulator do the same job as the reversible regulator in the 706 ?
If not, what exactly is its purpose and is it essential to have it fitted ?

Thankyou.
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Old 25th May 2020, 5:50 pm   #2
198 kHz
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Default Re: GPO Jack unit 1B and regulator 6B

It was to prevent transmitter noise on short exchange lines or PBX extensions.
The jack units in my TRS used them, as we were just across the road from the exchange.
My recollection is that there wouldn't necessarily be noise without it, but without cuent limiting by the 6B the transmitter insert in the headset could 'fry' in the long term.
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Old 25th May 2020, 8:40 pm   #3
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Default Re: GPO Jack unit 1B and regulator 6B

Thankyou 198.
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Old 26th May 2020, 12:21 am   #4
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Default Re: GPO Jack unit 1B and regulator 6B

..👍🏽
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Old 28th May 2020, 12:44 pm   #5
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Default Re: GPO Jack unit 1B and regulator 6B

Quote:
Originally Posted by 198 kHz View Post
It was to prevent transmitter noise on short exchange lines or PBX extensions.
The jack units in my TRS used them, as we were just across the road from the exchange.
My recollection is that there wouldn't necessarily be noise without it, but without cuent limiting by the 6B the transmitter insert in the headset could 'fry' in the long term.
How did that regulator work? Was it just 2 resistors to make voltage and signal loss like a longer line? Never seen that, but I have seen some fried carbon transmitters.

dsk
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Old 28th May 2020, 6:20 pm   #6
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Default Re: GPO Jack unit 1B and regulator 6B

Here's a picture of the regulator. I've taken it out of the unit but it fits between T11 and T17 on the circuit board. It appears to be two similar-looking components soldered to a coil. More than that I really can't say!
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Old 28th May 2020, 7:12 pm   #7
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Default Re: GPO Jack unit 1B and regulator 6B

Quote:
Originally Posted by Sparks View Post
It appears to be two similar-looking components soldered to a coil.
The "two similar-looking components" look like diodes to me - in opposed polarity.
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Old 28th May 2020, 7:36 pm   #8
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Default Re: GPO Jack unit 1B and regulator 6B

Quote:
Originally Posted by Dave Moll View Post
Quote:
Originally Posted by Sparks View Post
It appears to be two similar-looking components soldered to a coil.
The "two similar-looking components" look like diodes to me - in opposed polarity.
Agree, but regular diodes in opposed direction would not be to much help, but as Zener diodes it could give a suitable voltage drop. Things like that makes me wonder how they did figure out the solutions.

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Old 28th May 2020, 8:53 pm   #9
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Default Re: GPO Jack unit 1B and regulator 6B

I'm afraid I haven't a clue. I just put wires and straps and things where the experts tell me. The circuit board in this jack is largely based on that of the 746 telephone, but I've never seen this regulator in a 746, unless it has a different design.
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Old 28th May 2020, 9:06 pm   #10
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Default Re: GPO Jack unit 1B and regulator 6B

I think that regulator is specific to the Jack 1B. I have a 1B with a similar one. The 700 series 'phones use a regulator of a completely different design.
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Old 28th May 2020, 9:39 pm   #11
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Default Re: GPO Jack unit 1B and regulator 6B

Thank you any way, one day we will find it out.

dsk
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Old 28th May 2020, 11:04 pm   #12
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Default Re: GPO Jack unit 1B and regulator 6B

Quote:
Originally Posted by Dave Moll View Post
I think that regulator is specific to the Jack 1B. I have a 1B with a similar one. The 700 series 'phones use a regulator of a completely different design.
The Vocabulary of Engineering Stores states "only used with Jack Unit 1B (not earlier 1a) and used to stop 'frying noise' when used wit a Headset No 1"
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Old 29th May 2020, 7:56 am   #13
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Default Re: GPO Jack unit 1B and regulator 6B

I wonder if the 3T earphone element had a problem with the jack unit ?
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Old 29th May 2020, 8:22 am   #14
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Default Re: GPO Jack unit 1B and regulator 6B

The 3T was possibly more sensitive.

When used continuously by operators on public exchange switchboards, the receiver may be too loud for comfort. Under these circumstances the sensitivity should be reduced by shunting the receiver with a Resistor, Carbon, No. 4, 150 ohms. When used at PBXs this shunt is not required since an 180 ohm series resistor is provided in the operator's circuit.

jack units for headsets were usually used on Key and Lamps.

https://www.britishtelephones.com/head2.htm
https://www.britishtelephones.com/jackunit1.htm

What we'd do without Mr Freshwater's magnum opus website, I do not know.
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Old 29th May 2020, 8:34 am   #15
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Default Re: GPO Jack unit 1B and regulator 6B

... and its companion archive of wiring diagrams from Sam Hallas.
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