My Homemade PBX (2002)

As a kid I was intrigued by telephones. I got hands on two old rotary phones and I wanted them to talk together. I wired them in series with a battery. Despite my dad telling me it never gonna work - it kinda worked. You could hear the other side just well! It just did not ring.

I've made a great effort in making the phones ring. At that time I did not know it needs 90V (fortunately - I'd probably hurt myself). I figured out it needs AC, but how do you produce AC with only a battery? I even made a hack to rapidly reverse polarity using a relay in self-oscillating mode, only to get shocked by the induced voltage by the relay coil and no ring.

(Now I see that maybe if I used the coil voltage it would actually ring!)

This great article brought back nice memories of tinkering with the phones.

This really looks like fun!