Heavily modified GEC (not GPO) 746, that isn't actually a phone as such...

[twocvbloke]

Speaking of confusing wires, erm, yeah, went about putting together what I have to see how things will work and, yeah, it's gotten confusing even for me...

Though some elements of it, particularly the bodge of having separate boost supplies for lighting the lamps for the Unlocked and Caller functions powered from a main 12v supply, I think I need some relays (could go solid-state with transistors, but I want clicky relays!!!) so I can have just one 24v boost supply to work from, otherwise things just become too over-complicated...

[twocvbloke]

Well, after spending most of the day yesterday blowing up the lower relay board in the previous pic & repairing it several times, it left me feeling pretty grumpy, especially when I finally noticed where I'd made the error (A short to ground due to my forgetting that the Common wire to the phone's lower lamps & red button is a common positive, not negative!), so I'm just going to leave this project for a few days for me to think things out better, plus I need more parts to make it work anyway, just a good job I didn't have the phone hooked up to the wiring, not sure what it could have done, but didn't want to risk anything anyway...

Still, that's what happens when you put things together on the fly, mistakes are made, but lessons are learned, well, usually the are... 

[twocvbloke]

Well, more parts arrived (at last!), one being a project box to use as the controller box with all the electronic gubbins which will make things a bit easier to keep tidy once I work out what I'll be doing circuitry-wise, also got a trio of A.P. Besson transmitters akin to the one fitted in the phone thing's handset, only not the "military" version (as they're red with a white stripe, akin to a "No Entry" road sign, and have the N.S.N. number), some wider terminal block strips with more connections (9x per strip) as the three red ones I was using were not enough, a couple of 24v 4x Relay boards, whether I need two I'm not sure, but always good to have a spare just incase of human error, and last but not least, a button, which if you've been on public transport in the past 20 years, you'll probably recognise as a door button, which I thought was appropriate as I'll be using it for a door-phone call button... 

Also dug out a speaker which I think was either from a set of Sony headphones that fell apart due to age, or a Turtle Beach gaming headset I pulled apart for spares, not sure, but it's a speaker so its' origins are moot, should work a bit better than a 4T receiver volume-wise...

Took me a while to figure out why the button didn't work though, the green and yellow wires from it are across the tactile switch, but nothing, no continuity when pressed, it was only when powering up the LEDs I found that apparently there's some smarts to it where it'll cut off the button when there is no power, which made sense as it occurred to me when riding on Northern Rail trains in Lancashire, if the button is not lit, the door is locked and the button won't do anything, so it's a lock-out system for safety on a bus, train, tram or the like... 

I should get on with figuring out wiring version 2, so I can get this project up and running...

[Key2871]

That's a great idea for a door bell alert.
And are you going to change the function of the smart switch? Or leave as is..

[twocvbloke]

The button will remain as it is, so long as it is powered to light the LEDs, the button works fine so no need to modify it, not that I could anyway as the workings are resined in place, so dismantling would be destructive... 

I may add some extra LEDs behind it to illuminate when pressed, apparently this button is an earlier revision of the manufacturer's creation, the later ones having additional LEDs that lit when the button was operated, which would be a nice feature to have...

[Key2871]

Ahh, got ya. Well you don't want to destroy the thing.
Besides having it out does work nice a door bell button, it shows up at least somewhat even in low light.
But I bet it lasts a while, given its a commercial type of deal. But you have plans on using your phone as it kind of was intended and that's cool as well. Nice work!

[twocvbloke]

I was running the button on 12v for testing (it's rated for 24v, which most commercial things like buses, trams & trains often work on for battery power) so the LEDs would probably be a bit brighter, could even just leave as-is on 12v depending on how I set up a different wiring scheme now I have more options (and more isolation between things!!) for connections and power, we'll see though...

As for using the phone as it was originally intended, well, not knowing its' original intention, it's just being put together for demonstration really, still got to work out what to do with the two buttons to give them some visible function, even if it doesn't actually do anything other than say switch between the lights when pressed (E.G., press "Transfer" and the "Assume" lights up & vice-versa), but that's other things to work out, as it'll probably involve latching relays and whatnot, something I've never done before, but it's one of the reasons I'm enjoying this project as I'm learning new things as I go... 

Oh, and the terminal strips, seems I forgot how to count, they're 10-position, not 9, I think I confused myself as I was going to buy some 9-way ones instead...

[Key2871]

Yes I know you don't know the true use of the set, but I think you have come very close to understanding things than most may have.
It seems rather clear that it was supposed to operate a electronic door lock among other things.
But it's cool that you've good as far as you have.

[twocvbloke]

I've not even thought of what to do for the lock part, might see if there's a small solenoid thing out there to operate when the button is pressed, but something to think of for later...

Last night I was looking at how I could arrange things inside the project box, got two terminal strips stuck in there now (rather cleverly stacked too, top row being removable as I glued it onto the cover for the bottom one so can access that one without much fuss), and trimmed down the corners of one relay board to fit snugly into one corner leaving room for other parts to fit into, though not currently sure what parts will be in there...

Also made up a crude power module with two of the boost regulator boards, one for 12v & one for 24v, joined together with some solid copper wire as busbars, though did manage to burn out another board trying to set its' power output, but turned out I'd dropped its' trimpot all the way to 0-Ohms and pop went a 6-legged part, glowed light a lightbulb briefly too...

Forgot to take pictures as I went, but I can do that later when I play around some more...

[19and41]

Here is an amazon search for the locks, referred to as an electric door strike.  It serves as the point the doors latch in the jamb and releases when a voltage is applied or removed, depending on the system used.

https://www.amazon.com/s?k=electric+door+strike&s=price-asc-rank&qid=1593951457&ref=sr_st_price-asc-rank