GEC MT 4150 Extension Telephone

[wds]

Thanks to Larry's eagle eyes, I now have a GEC Extension Telephone.  Quite large, and in very good shape.  I won't have time to polish it up for a few days, so I decided to go ahead and post some pictures.  Now all I need is a couple of the extension phones to complete the system.  Top half kind of looks like the Pyramid phone.  Anyone know if this can work as a phone by itself?

http://www.britishtelephones.com/gec/tel1s.htm

[wds]

This phone sure cleaned up nice.  In perfect shape, looks like it should just plug in and work. 

[twocvbloke]

I'm always intrigued as to how those and later Planset systems worked, I can't figure it out myself, but they seemed to have been popular at the time where needed...

I want to get a 700-series based planset at some point to have a play, cos I've never even seen one in person...

[LarryInMichigan]

Dave,

It looks great!  The top half IS a GPO "pyramid" phone.  It looks to have all of the necessary components, other than a ringer, so it should be usable as-is. 

This phone should be nominated for the find of the month.

Larry

[Owain]

check whether it's a bellset 39A or 44. The BS No. 39 differs from the BS No. 44 by having the indicator to the right of the sliding switch, a Buzzer No. 24A and chromed press buttons.
http://www.britishtelephones.com/bellst39.htm

http://www.britishtelephones.com/pstconv1.htm#248

[wds]

From comparing the pictures, I believe I have the Bellset 39.  Chrome buttons also.  There is a clear cover to the right of the sliding switch, held in place by the four screws.  Not sure what that might be for, unless something lights up behind it.

[Owain]

From comparing the pictures, I believe I have the Bellset 39.  Chrome buttons also.  There is a clear cover to the right of the sliding switch, held in place by the four screws.  Not sure what that might be for, unless something lights up behind it.

It's for the Indicator No. 3900A
This is a 3000 type relay, having one change-over spring-set and flag signal attachment.  The relay is mounted on the right-hand side of the switch on a special bracket and its purpose is to give an indication when an extension-exchange call (or vice versa) has terminated.  The signal is visible through a glass window in the bell-set cover situated above and to the left of extension No. 1 press button.  The flag consists of a metal plate, pivoted to the relay frame on two arms.  The plate is divided vertically into halves, the left-hand half being black and the right-hand half white.  The right-hand half carries the word ENGAGED in black vertical lettering.  The operation of the indicator is as follows:-

(a) When the indicator is normal, the black section of the flag is immediately behind the window.

(b) The indication is operated by the exchange current flowing through the extension telephone.  It is designed to operate with 30ma and to hold with 50mA when the extension dials.

(c) When operated, the white section moves into position behind the window, showing ENGAGED.  The indicator cuts out the bell circuit at the "main", thus preventing tinkling of the "main" instrument bell when the extension dials.  A further advantage lies in the fact that impulse distortion, due to the bell and condenser being across the line, is eliminated.

[wds]

You're right.  I took the phone apart, and there is a flag that pivots left - right, one side black, the other white with "engaged" .  Thanks for the info!