<font face="Verdana, Arial" size="2">Originally posted by Keyset6:
I think that's cool the step system is still working. That's neat how you can patch audio through the switch, although as you said the audio might not quite be 30-15khz. It was almost like those step COs had character back then, the dial tones & ringing signals varied with different offices, and even slight differences could be heard with the same "model" CO. I'd like to find history book about Central Offices & telephony development in general. [/B]</font>
Yep..
The switch has been updated a bit over the years, for instance, there is a standalone module (teltone M-106?) that allows passcode protected access from the outside via a directly connected POTS line.
Special features include seizing ringing incoming CO lines from any phone in the system, paging, and monitoring of various audio busses, and I think it will do transfer of incoming CO lines to any extention as well..
For books, you want to look for the Bell System publications "The History of Science and Engineering in the Bell System". There is a whole series of them, now out of print, covering switching technology, transmission technology, etc..
