746 planset phone

[trevwgb]

Hi
I know you all know this - I have this phone / planset which was in my father-in-laws shop in Godalming and removed in the 80's. I have the basic phone working normally so it seems in reasonable order.
I have the circuit & N diags. but it is not clear to me where / how the power supply connected in to the system.
Also the bottom of the planset has no base. I presume that's gone missing?
Assistance much appreciated as always
Regards
Trev

[AndiiT]

Hi,
The Planset 625 (to give it it's correct name lol) was used as a small Manager/Secratary/Intercom/Exchange switching system and more information can be found at the following URLs http://www.britishtelephones.com/plans625.htm and http://www.samhallas.co.uk/repositor...4000/N4509.pdf
Most of the wiring digrams can be found and downloaded form Sam Hallas' site.

Some Plansets used the Red and Green conductors for the power supply, but there have been changes to these over the years - be very careful not to reverse the polarity of the supply or damage will result to the planset. I have lots more information/expertise on this particular type of planset, having had installed one in two different properties of mine over the years, feel free to PM me if you need any more help/information.

Whoops I didn't see that you already had the diagrams, do you need to know how/where the power supply is connected so that you can use the Planset to it's original intended purpose?

Regards
Andrew

[trevwgb]

Hi
Thanks Andrew - yes my immediate practical problem is where the power supply connects - I read about the danger of reversing the polarity so realize I need to watch what I am doing here
Regards
Trev

[AndiiT]

Hi,
The power supply connects as follows, Negative to Green (or Blue) and Positve to Red (or Orange) of the Line cord.
The colours in brackets only apply if the Blue and Orange conductors are connected to T16 and 20, respectively at the Planset end. You shouldn't harm anything by mixing up the green or blue and red or orange leads but as mentioned before make sure that the polarity is correct.

The Planset uses a 10 Volt power supply, a PP3 (6F22) battery will suffice for test purposes (and also for general use if you don't have access to mains derived power).

To clarify a little more here are some of the "basic" connections that you will need to make.

Power -ve Green (Blue)
Power +ve Red (Orange)

Exchange B leg Blue (Brown)
Exchange A leg Orange (Slate)

Extension B leg Green/Brown (Orange/Slate)
Extension A leg Red/White (Green/Brown)

I believe that earlier versions of the Planset had the line cord colour coding shown in brackets.

NOTE - The Yellow (or White) Extension to Exchange lamp will only light if the Planset is connected to an active exchange line when the extension is in use and should flash in sympathy with the incoming ringing cadence on an incoming call when the ext to exch mode is selected..

In the original wiring diagrams the Bells are series wired, I have details of a couple of small (unofficial) modifications to allow the bells to be parallel wired and also give the option of using a more modern phone as the extension end of the Planset.

Regards
Andrew