Sterling Telephone and Electric Co. wall phones - UK Vintage Radio Repair and Restoration Discussion Forum

richrussell · 6th Dec 2008, 10:14 pm

I've acquired two wooden cased wall mounted telephones, made by the 'Sterling Telephone and Electric Company' - I'm guessing around 1920-1930.
The model number is U125.

I know these two can be connected together to form an intercom circuit (with the addition of an external battery obviously), but can't figure out how. There is a hook switch, bell, signalling pushbutton and of course a magnetic earpiece and carbon microphone (mounted on the box). There are no inductors other than the bell relay and magnetic earpiece.

There are three terminals inside - and I've worked out that the microphone and earpiece are in series, and connected to terminals 1 and 3 when the earpiece is off hook. So simply connecting terminal 1 from one phone to terminal 3 on the other, and a battery in series between the remaining terminals 1 and 3 gives the audio (very faint and crackly, but it's there). I've established connecting a battery from terminal 1 to terminal 2 rings the bell when the earpiece is on the hook.

Now, I'm sure these have a standard wiring system in common with many telephones of their era, and know GEC bought the company and marketed them under their own model number scheme later. But what I can't find out is how I connect them up for the bell on the other phone to ring when the pushbutton is pressed on the first one. Also I'm sure I probably shouldn't just run DC through both the earpieces and microphones - maybe a transformer to couple them is what should be used?

Any ideas?

Rich.

dagskarlsen · 7th Dec 2008, 10:50 am

I have some Ericsson intercom telephones with the transmitter and receiver in series,
theese are connected with 1 pair, and each phone has 3V battery in series with the transmitter and receiver.
When going on hook the hookswitch a single pole switch change from ringer too speach- circuit. a pushbutton gives battery voltage to line, (shorts the receiver and transmitter).

The other one has a posibility of putting in more batteries to ring thru longer lines.

Could you please send some photos, or wiring-diagrams?

May this help:
http://img.photobucket.com/albums/v4...com_8lines.jpg

dsk

dagskarlsen · 7th Dec 2008, 11:56 am

http://img.photobucket.com/albums/v4...leintercom.jpg
This is the simplest I have used, works well in shorter distances.
A on one telephone conects to B on the other.
Batteries on mine were 3 Volts. Rising the voltage too much will harm the transmitter.

dsk

richrussell · 7th Dec 2008, 2:03 pm

Many thanks - that does shed some light on it. A bit more research has revealed that these may well actually be based on the Ericsson designs and probably contain parts made by them.

I'll try to get some photographs this afternoon and have another go at working out where the wiring goes. It's not easy to follow round as all the cotton wrapped wiring is the same colour and tied in tight bundles. The bell seems to be connected to terminal 2 only, so certainly that terminal must be connected to something for it to ring.

6th Dec 2008, 10:14 pm	#1
richrussell Heptode Join Date: Jul 2008 Location: Selby, North Yorkshire, UK. Posts: 979	Sterling Telephone and Electric Co. wall phones I've acquired two wooden cased wall mounted telephones, made by the 'Sterling Telephone and Electric Company' - I'm guessing around 1920-1930. The model number is U125. I know these two can be connected together to form an intercom circuit (with the addition of an external battery obviously), but can't figure out how. There is a hook switch, bell, signalling pushbutton and of course a magnetic earpiece and carbon microphone (mounted on the box). There are no inductors other than the bell relay and magnetic earpiece. There are three terminals inside - and I've worked out that the microphone and earpiece are in series, and connected to terminals 1 and 3 when the earpiece is off hook. So simply connecting terminal 1 from one phone to terminal 3 on the other, and a battery in series between the remaining terminals 1 and 3 gives the audio (very faint and crackly, but it's there). I've established connecting a battery from terminal 1 to terminal 2 rings the bell when the earpiece is on the hook. Now, I'm sure these have a standard wiring system in common with many telephones of their era, and know GEC bought the company and marketed them under their own model number scheme later. But what I can't find out is how I connect them up for the bell on the other phone to ring when the pushbutton is pressed on the first one. Also I'm sure I probably shouldn't just run DC through both the earpieces and microphones - maybe a transformer to couple them is what should be used? Any ideas? Rich.

7th Dec 2008, 10:50 am	#2
dagskarlsen Heptode Join Date: Jan 2008 Location: Hakadal, Norway Posts: 642	Re: Sterling Telephone and Electric Co. wall phones I have some Ericsson intercom telephones with the transmitter and receiver in series, theese are connected with 1 pair, and each phone has 3V battery in series with the transmitter and receiver. When going on hook the hookswitch a single pole switch change from ringer too speach- circuit. a pushbutton gives battery voltage to line, (shorts the receiver and transmitter). The other one has a posibility of putting in more batteries to ring thru longer lines. Could you please send some photos, or wiring-diagrams? May this help: http://img.photobucket.com/albums/v4...com_8lines.jpg dsk Last edited by dagskarlsen; 7th Dec 2008 at 11:05 am.

7th Dec 2008, 11:56 am	#3
dagskarlsen Heptode Join Date: Jan 2008 Location: Hakadal, Norway Posts: 642	Re: Sterling Telephone and Electric Co. wall phones http://img.photobucket.com/albums/v4...leintercom.jpg This is the simplest I have used, works well in shorter distances. A on one telephone conects to B on the other. Batteries on mine were 3 Volts. Rising the voltage too much will harm the transmitter. dsk

7th Dec 2008, 2:03 pm	#4
richrussell Heptode Join Date: Jul 2008 Location: Selby, North Yorkshire, UK. Posts: 979	Re: Sterling Telephone and Electric Co. wall phones Many thanks - that does shed some light on it. A bit more research has revealed that these may well actually be based on the Ericsson designs and probably contain parts made by them. I'll try to get some photographs this afternoon and have another go at working out where the wiring goes. It's not easy to follow round as all the cotton wrapped wiring is the same colour and tied in tight bundles. The bell seems to be connected to terminal 2 only, so certainly that terminal must be connected to something for it to ring.