Plan 105 with external extensions

[TonyDuell]

The Converter Ringing 9A is only powered when a 'calling' key is pressed (battery -ve is then connected to the Converter Ringing 9A via contacts KA2 or KB2 in the Planset, see N4507 for more details). It was possible to run the Planphone system off a battery rather than the mains power supply (Power Unit 53B), the official battery was 8 'Flag' cells in series. I've run mine off 8 D cells in series at least for testing/demonstration.

[AndiiT]

Originally Posted by Dave Moll

....When switched to "extn to exch", the buzzer in the main sounds as well as all bells? Is this what should be expected? ...

Yes and no, in the Plan 107 external you could strap the Planset to allow the bell to sound as well as the buzzer when "switched through", this was never an option on the Plan 105 external set up - however as you have strapped your A leg and earth to allow ringing on an incoming call this is the reason that your bell and buzzer sound simultaneously.

Andrew

[Dave Moll]

Sorry, Andrew, I was mistaken about the bell ringing in the main. Listening a little more carefully while muffling the sound of the extensions ringing, I realise that only the buzzer in the main is sounding, not its bell - despite having a capacitor between the A leg and earth.

[TonyDuell]

I seem to remember that's what it should do. Diagram N1450 has a comment to this effect too. You get the buzzer sounding at Main if the extensions are ringing.

[Dave Moll]

It seems that even the lack of ringing was down to that broken wire, and the connection between A leg and earth wasn't needed after all.

While trying to track down a severe crackle that has developed while switched to the default speak to extension, I disconnected the capacitor that I'd inserted between the A leg and earth. Lo and behold, the main still rings on "spk to exch", and the extension rings, with the main buzzing, on "extn to exch".

Oh, and the crackle is probably down to the switch contacts, but my Servisol 10 has chosen this moment to run out without warning! Project on hold until a new can arrives.

[AndiiT]

Originally Posted by Dave Moll

...and the connection between A leg and earth wasn't needed after all.....

That's interesting and suggests that I may well have a problem with my own Plan 105 "external" demo set. I may have to dig it out and do a bit of fault finding, in between still having to go out to work to keep the wheels of the broadband industry turning.
I'm off work till Friday so may well have a play about in the next couple of days.

Andrew

[TonyDuell]

I seem to remember that when I worked through the Plan 105 External circuits, you do need the A leg to be earthed for the ringing circuit to be completed. It was assumed this was done at the exchange, but when I was running the setup on a line simulator on the bench it did not ring until I'd made that connection.

Of course the A leg would normally be essentially earthed at the exchange so it will work without extra connections on a normal telephone line.

[Dave Moll]

I'm beginning to wonder whether the A leg is inadvertently shorting to the earth (which isn't physically earthed by the way, continuity merely maintained within the setup). I'll do a bit more continuity checking.

As far as earthing at the exchange is concerned, I should say that all my testing is done on extensions of my house PABX.

[Dave Moll]

Originally Posted by Dave Moll

I'm beginning to wonder whether the A leg is inadvertently shorting to the earth.

Resistance measures as ∞ in all switch positions, so it would appear not. As a certain Alice would have said, "curiouser and curiouser".

[WayneL74]

Originally Posted by OscarFoxtrot

Do you have higher-res or vector versions for printing, please?

Have sent you a PM

Regards,

Wayne