N2128H1T telephone

[Sparks]

This 700-style telephone arrived this morning via eBay. I've not seen one like it before so I hope somebody can give me a clue as to its likely origin and purpose. There is wire mesh fitted in the bell gongs and under the board, so perhaps a tropicalised unit ? I won't be attempting to rewire or convert it, just a clean and polish.

[Sparks]

More pictures.

[Nickthedentist]

Very nice, and unusual to find a 2-transistor "magneto" ring generator as opposed to a hand-cranked one.

ETL = Ericsson Telephones Limited. The N...... number is also typical of Ericsson phones.

Is the case a standard 706-type one, or is it bigger to accommodate that huge transformer and the two transistors?

As usual, Bob Freshwater has the answer: https://www.britishtelephones.com/ericsson/n2128.htm

This suggests that it was a late-1960s phone designed for old "CB" (etc.) systems which were likely to be modernised into "auto" systems. The phone could then be converted rather than replaced.

Nick.

[Pellseinydd]

Originally Posted by Nickthedentist

Very nice, and unusual to find a 2-transistor "magneto" ring generator as opposed to a hand-cranked one.

ETL = Ericsson Telephones Limited. The N...... number is also typical of Ericsson phones.

Is the case a standard 706-type one, or is it bigger to accommodate that huge transformer and the two transistors?

As usual, Bob Freshwater has the answer: https://www.britishtelephones.com/ericsson/n2128.htm

This suggests that it was a late-1960s phone designed for old "CB" (etc.) systems which were likely to be modernised into "auto" systems. The phone could then be converted rather than replaced.

Nick.

There appears to be an error on Bob's webpage. This circuit doesn't have any provision for converting the phone to automatic - where are all the terminals that the dial would connect to? CBS3 was a 'GPO system' developed in the early 1920's and of the GPO's 472 exchanges, only half a dozen exchanges of that type survived until 1960 and all had gone by 1963. I'm lucky enough to have the only survivor. Webpage mentions CBS1 systems but those had long gone by 1960 plus there is no provision for the bell which was earth connected via the switch hook to the 'A' leg of the line. It could be used on a CB circuit (or auto circuit for incoming only) provided the 1.8uF capacitor was fitted but why go to the expense of a local battery magneto phone. Note that it doesn't have the 'standard' 706 circuitry/PCB

This telephone is just a basic magneto telephone for use on circuits where a magneto telephone was used. I have several of them acquired over the years. Not a rare item. Ideal for a 'point to point' intercom.

[Sparks]

Thanks Nick, I'll pore over the Freshwater Files! Two more pictures in the meantime. The transistor block lifted out quite easily. The case is a regular 706 type, as far as I can tell.

[Nickthedentist]

Thanks for the info/correction, Ian.

And yes, Sparks' pics in post 5 clearly show the socket for the reversible regulator found in the 706 etc., but permanently shunted by Cs and Rs soldered to its tags.

[Sparks]

Thankyou both for the information. I don't have any use planned for the phone so it will be merely decorative once I've rebuilt and polished it. It came with a handset bracket to allow wall-mounting so that might be its destination.

[dagskarlsen]

Nice find!
Ineresting ringer generator, anybody who knows if it actually gives AC between 25 and 25 hZ witch would be OK for most magneto telephones??

dsk

[Sparks]

Looks better for a polish, even if it isn't functionable on a normal phone line. I just need to find two bolts to hold it together - hopefully some at home somewhere.

[JohnBHanson]

Anyone know what is the reason for R2 in the ringing generator circuit (22ohms)

Thanks.