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and very rarely ever needs repairs, once you fix them." - Dan/Panther

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Miniature 10-line telephone exchange using 22 relays

Started by Owain, January 29, 2012, 10:21:34 AM

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Has anyone made this? If so can they post a video to YouTube and link it here?

I am thinking of putting this together..


I can now report that the 10 line exchange is now working...tests so far have shown no operational issues.

The final circuit now uses 32 relays mainly due to dispensing with the BCD calling line identifier and substituting it with individual calling line relays with lockout function. The ring cadence generator is now a double multivibrator which produces the standard UK/AUS 0.4 on- 0.2 off - 0.4 on - 2.0 off pattern. The original dial tone and ring tone feed arrangement is totally useless and has been replaced with a transformer feed arrangement. My 48V DC power supply also incorporates a 25Hz @ 80V ringing supply so the DT and RT are at this frequency.

My final arrangement consists of 4 boards all using wire-wrap technique. Board 1 holds the 10 line relays and the 8 relays in the dial pulse counter. Board 2 holds the A and D relays plus all other control relays. Board 3 is the ring cadence generator. The 4th board simply holds the tone feed transformer because there was no room available on the control board - where it would normally have been located.

When I get all the circuits tidied up I will post again.




I would LOVE to see a video on that if possible!


Sounds Great! When it is all ready would you post some pictures? I for one, would like to see it. I am sure others would be interested too.
Harry Smith
ATCA 4434

"There is no try,
there is only
do or do not"



Go to page 41
has a LOT more information with more high quality images for this little diagram!


EDIT: Entire document and Pages 41-45 attached as a PDF files


Quote from: dylanc4 on February 12, 2019, 01:24:00 PM
Go to page 41
has a LOT more information with more high quality images for this little diagram!

Note also the corrigenda in the following issue, which I included in my original scan.


Well, I have been prompted to do something about getting something posted on my arrangement of this project so I will start with a sketch of the line relay and binary counter stage. I will post other docs and pics as I can get around to it. It is a pdf with 2 pages so you will have to join them to see the full diagram.

Jim Stettler

You live, You learn,
You die, you forget it all.