Quote:
Originally Posted by majoconz
If you can hunt out an old booklet called "Out of Thin Air" published by the old Practical Wireless, there is an article in there on connecting two phones together over twisted pair. I needs a 9v battery in each unit and a small bit of Veroboard with a 741 to give the gain. It doesn't ring the bell, the 741 is made into an oscillator to make a loud noise in the other end earpiece.
If you can't find the booklet I'll scan it and send it to you - pm me with your email address.
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Page 20 here
http://radio-amador.net/pipermail/cl...hinAir1980.pdf
Also attached in case that URL disappears.
I've been looking for that circuit for 27 years!!
- I thought it was about 1988 it was published. Perhaps it was in an updated version.
Even less technological was the "Stanophone" which comes up on ebay occasionally.
http://www.unipartrailexpress.com/product.aspx?37182
The 10 line telephone exchange with 22 relays is attached if I can find the file. Note the corrigenda on the last page. Also a Cook Abbott ringdown circuit.
As the OP has a working Panasonic system and probably working telephones, however, the simplest thing will be to get them to work together as originally desired.