A Western Electric / Bell South payphone with the 1996 US olympics
logo, you see these on ebay from time to time. It has the high
voltage coin retention coil thingy intact, a functional dual-ringer,
32 series Chassis.
( I will put some photo's up somewhere under my projects on my
gopherspace's root menu)
In any event, I've got it hooked up to a raspberry pi running
asterisk via a switchpi module, and I have that, in turn connected to
SDF's voip system. I sent SDF some extra dollars so I can have
outgoing calls. I'd rather pay them than anyone else anyway. And it
seems to be mostly functional now!
I did end up having to boost the voltages a bit because the ring
voltage comming out of the switchpi wasn't quite enough to make the
payphone ring.
The vanilla ring-voltage turned out to be around 30V - not sure what
current it could provide but I can't imagine it being very much. It
just kind of tickled the solenoid, which would vibrate a bit, but not
quite enough to hit the bells of the ringer.
I took a stab at trying to boost this voltage by means of a little
circuit. I had an oscillator circuit still assembled on a breadboard
for my synthesizer project, so I put some bigger capacitors in there
to tune it to around 20Hz, which should be roughly equivalent to the
frequency of a ring, and used that for testing and developing a ring
booster circuit. I used a transformer from an old wall-wart and
wired it up backwards - of course the current draw is way too high,
the coil looking like a near-short to the poor oscillator, causing
it's voltage to drop to nil. I wired up a simple pre-amp circuit to
put in front of it, but in the end none of the itty bitty transistors
i had in the junk drawer ended up being able to handle the current.
So in the end I just ended up buying a commercial ring booster, which
I wired up today, and the payphone now rings in it's maginificent
double-ringer glory!
I was surprised to find that the ring booster was way expensive! POTS
equipment has gotten expensive! Surely a consequence of the drop in
demand.
There's still a bit of an issue i have to work out with incomming
calls from SDF not being routed correctly within my asterisk dial
plan, but that should be easy enough to fix.
In any event, if you want to leave me angry voicemail (or nice
voicemail? i just assume it'd be angry I guess :P) - give SDF voip
ext. 2067 a ring! (there is currently a small asterisk - side issue I
have to fix with incomming calls - should be fixed soooon though)
