M2A2

http://www.siliconchip.com.au/

Hello Austin, I for one found your designs interesting having designed and built a few similar phone systems myself over the last 35+ years starting with a 10-line uniselector based PAX. I was particularly impressed with the audio transformers used as the transmission bridge in your original 2-phone link as proved a point that I had wondered about but not actually tried. Obviously it works but is there a problem with the core saturating due to the DC current in the primary winding? You mention that you had a 1996 version based on relays; do you still have that circuit diagram? Andrew