[rescue] Creating/Simulating/Emulating an old 1970s Bell Telephone Network

James Fogg James at jdfogg.com
Mon Aug 15 22:45:21 CDT 2005

>  I'm wondering if anyone has information or pointers
> regarding the above-mentioned topic. I'm teaching a
> Data/Voice Communications course this fall, and in my efforts
> to convey some deeper understanding of communications (plus
> expose these students to things like modems, rotary phones,
> even have the opportunity to try out classic coloured box phone
> phreaking) I was brainstorming in this area.

If you want to duplicate the actual Bell system, you have to span
several tiers (long lines, exchanges, etc.) and several generations of
electronics (or mechanics in the case of Strowger switches). It would be

>  I'm looking at eventually implementing the CO, switches, and
> end devices (be it an off-the-shelf phone, mock-up payphone,
> or whatnot).. and to intentionally make it operate on
> frequencies, so it can be manipulated...

You could acquire an old switch like a Siemens hybrid or a modern AT&T
5ESS with SS7 protocol. But it would be much simpler to find an old PBX
or key system that supports type 500/2500 phones (POTS phones). There
are many Stromberg-Carlson small exchange switches around too.

>  Any recommendations? Web sites, books? I figure this will be
> as much a learning experience for me as it will for my students.

The web. It's well documented.

You could also build simple phones from carbon mics, simple earpieces
and batteries. Add a switchboard for routing, then maybe add a strowger
and dials. The facinating thing about the phone system is that the first
phones with dials (early 1930's) are still supported. That is why you
can dial the operator by pressing the switch-hook 10 times quickly.

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