My Homemade PBX (2002)

by rickcarlino • 3 months ago

25 5 3 months ago

janci• 3 months ago

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.

xtiansimon• 3 months ago

“I figured out it needs AC, but how do you produce AC with only a battery?”

Really? I too toyed with two old phones in my yu’t (I had two push-button phones, took out the keypad and put in a single push-button) and I powered it with a 6V DC lantern battery.

Now, I trust your research to how a phone system really works, but I don't recall a trouble driving the ringer coil with that DC 6V power. I recall being surprised and delighted the phone was designed to work with only the RJ-11.

jakzurr• 3 months ago

This really looks like fun!

pstuart• 3 months ago

For some time I was a phone tech in the age of digital PBXs and phone systems were critical lifelines. It's changed so much now that a desk phone is an exception rather than the rule.

anonymousiam• 3 months ago

I did some phreaking as a kid (in the 1970's), but stopped when I turned 18. I learned a lot about phones in the process, and spent most of my career doing telecommunications engineering.

This article is from 2002 when it was probably still a lot cheaper to roll your own PBX than to buy one.

For the past seven years, I've been running FreePBX in a VM (in the same embedded, fanless server that hosts my OpenWRT router). I've got three full-featured VoIP desk phones with way more capability than the author's, and with a lot less effort.

https://www.freepbx.org

My Homemade PBX (2002)

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