BT713 Pendant telephone look-alike

[Sparks]

Good morning. Some years ago I bought a couple of these in a second hand shop. They have the metal base plate of the 713 but the similarity ends there. The ABS cradle is replaced by what looks like heavy duty cast metal. The handset has an eight core coiled cable, a black momentary switch at the top and both earphone and transmitter are 2400 ohm type 4T units.

Does anyone have any idea what their likely purpose would have been ? Thankyou.

[AndiiT]

Hi,
Ship's or mining use perhaps.

I've taken a look on Bob's Telephone file but can't find anything there. Maybe a picture of your phones would help.

Regards

Andrew

[russell_w_b]

From your description they're sound-powered. Any identification or markings on them?

[Sparks]

Some pictures here. Taken on this phone so not brilliant quality.

[AndiiT]

Hi again,
Looking at the pitcures they are possibly some kind of door phone for a flat entry intercom system.

Andrew

[OscarFoxtrot]

I don't think they're domestic intercoms. Entryphone (tm) used to do a telephone that was very similar to a GPO handset but a different base, but domestic intercoms would have a buzzer.

Push to talk switches are usually used for noisy environments and I think naval or industrial use is more likely, perhaps for making announcements over a public address system. Possibly press the handset button to make the announcement, then release the button and stay on the line and anyone lifting another handset can respond handset-to-handset.

[Sparks]

Thanks everyone. I guess the cast-metal cradle does suggest a heavy/dirty industrial application. However, the handset merely rests on the cradle and isn't gripped which makes marine use unlikely. Perhaps they were intended for mining or oil drilling.

[McMurdo]

might it just be one of those phones in an unmanned reception that buzzed the operator as soon as you lifted it? They still do that sort of thing today but of course they're programmable to dial an MF code.

[AlanC]

Hi,

I worked for Pye Telecom in the late 70's and we supplied them as an optional accessory for two way radio systems. They could be connected directly to a radio base station, or to a base station remote controller. The hook switch in the base was wired to cut out the radio speaker, when the handset was lifted, for privacy.

We engineers all had the same handset in our toolkits, known as an engineers handset (EHS), so if you were sent to a remote mast site, you could plug in to the transmitter/receiver rack and carry out test calls.

The 2400 ohm mic insert was used on almost all of our equipment at that time including the standard fist mic and the 'tulip' mic that was used with the RTC controller. It was only really superseded when the electret inserts came along in the 80s.

The last ones identical to spark's pictures that I saw were being scrapped from a police control room that was being refurbished around about 2002; I liberated a couple from the skip and made a very handy domestic intercom out of them!

Alan

[Sparks]

Thanks Alan. Now I know!