Reversing the regulator in a 711 telephone

[trevwgb]

Hi All
I am attempting a mod on a 711 telephone to link it to an Irish AB box. The instructions state to "reverse or remove the regulator." Having now worked out which bit is the regulator ( had not come across one of these before ) I find that it is soldered to the printed cicuit so "reversing" it is not a practical option. I am trying not to wreck the phone, which I suspect will happen if I try to unsolder and remove it and will clearly happen if I try to cut the connections to the board. Are there any other options to achieve what is required, while leaving it in situ?
Thanks
Regards
Trev

[JohnBHanson]

You should link the inner three connections and cut the outer two.

[TonyDuell]

Are you sure it's soldered in? In a 711 the regulator is a little PCB containing a couple of resistors, a special resistor lamp with 3 wires and a metal rectifier stack (a total of 9 connections).

Oriignally the telephone had a moulded plastic base, an edge connector for the regulator was part of this. Certainly later 706s (and maybe 711s) had a PCB for the rest of the electronics, the regulator PCB plugged into 5 contacts soldered to this.

As John said, reversing the regulator (meaning turning it upside down so what was the top edge then goes into the edge connector) makes no connection to the outer 2 contacts and shorts the middle 3 together.

Can you post a photo of the insides of your telephone just in case it's not a normal 711

[Oldcodger]

Possibly, I'll be corrected, but the special resistor lamp was a thermistor designed to match the length of the line to the optimum line impedance on lines of varying length, for Central battery operation. For local battery operation on older (eg magneto & Country Satelite ) exchanges, it was reversed to take the self regulation facility out of circuit.

[BigClick]

As predicted here is a correction

The tele 711 us a wall mounted version of a tele 706 or 710
The regulator was to regulate sensitivity when the subscriber termination was close to the exchange. Without it the instrument could pick up RF from local sources such as taxis. When the distance increased the regulator was intended to be reversed.

Here is a description of the tele706
http://www.britishtelephones.com/t706.htm
From there you can find the 710 and 711

Also here is a wiki explanation...
A feature of the 706 was a regulator that could be used or not. The idea was, that if the subscriber was close to the exchange, the regulator would reduce the sensitivity, as it had been found that this telephone was too sensitive close to the exchange and also had a propensity for picking up radio broadcasts, from strong stations, mainly taxis. The purpose of the regulator was to vary the amount of ac speech current flowing through the transmitter and receiver, to prevent it being considered too loud by subscribers on short lines. The regulator consisted of a network of rectifiers, diodes, resistors and two thermistors.

The regulator could be removed from circuit, for customers not close to the exchange. This was achieved by turning it upside down, which substituted a shorting link instead of the components. In practice the unit was normally left in circuit. Compare this with the inside of a 746 where the regulator is permanently built in.

[trevwgb]

Hi All
Many thanks - all this was very helpful and informative ( I think I might call turning it upside down inverting it rather than reversing it! ) - hence ,at least part, my confusion.
Regards
Trev