So, I got a payphone.

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)

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