From: feotus@yabbs
To: all@yabbs
Subject: Out Of Band signalling 101
Date: Sat May  7 11:52:33 1994
after digging thru my rusty trusty telecommunications bible..

ht:  well why would I worry about a COCOT with OOB, since all the charging 
etc.. takes place inside it and it's just another POTS line to it?  But I 
can see where you mean acces to wires is easier, almost laways something 
exposed.  On fortress phones it's difficult, unless you have a concrete 
cutter or something in your pocket.

first inline band signalling -  it is basically control signals from 
office to office INSIDE the voice bandwidth ~~ 300-3100Hz.  These are like 
the 2600Hz signal for the now dead blueboxes, and the 2500Hz for RedBox 
tones.

out of band-  is when the line carries the normal voice bandwidth, and 
also a narrow signaling band, usually only at a single frequency. For 
insance the CCITT Signaling System no. R2 (CCITT is sorta like 
international standards) uses a signalling band of 3825Hz (+-4Hz) of rit's 
OUT of band signalling.

most of you probably know that stuff already.
 
in order to use out of band signalling tho, the telco has to install more 
electronics on both ends.  Now at the local office, that's no problem, but 
that means they need to add it to the payphone if their going to use it 
between them and the office.  So older ones are no problem usually, it's 
the newer ones they are installng, tho I have found that not all of them 
use it.
 
the out of band control signlas are sent thru the voice channel, so ou can 
no longer put a tone generator to the receiver and have it go thru.  You 
need to patch either into the electronics of he signaller itself, or into 
the wires.  This is difficult on payhhones to say the least.
 
I havent figured out waht frequency the telco's are using now for ot of 
badn signalling, as the telco around here isnt using it yet, so the
  I know who work there don't know yet.