IBM System7use of Teletype as console 2547

Not exactly a PBX (a good deal smaller than some, actually!)... But a small-town phone switch that I scrapped out had both a 2741 for conversational access to an IBM 360 (model 91?) and some sort of RJE system that transmitted long-distance billing data over the same data link (a mid-size IBM box with a synch modem on top.)

I'm told the RJE system was originally a card reader printer arrangement, later switched over to a Mohawk Data Systems tape system. When I got around to wrecking the place, we had a start-stop tape drive (Kennedy) on the switch that recorded billing data -- that tape was later mounted on the RJE system for transmission to the billing wenches.

Not sure how the data got from the switch (a purely mechanical beast) onto the tape. Data representation in the switch was a serial pulse train representing the number dialed. DTMF dialing was accomplished with a "black box" on the line finder that converted DTMF into dialing pulses. A similar black box took the pulse train and sent it over to the tape subsystem.

The whole thing (except for the ring generators) ran on 48 volts DC and was built by Western Electric in the 1950's. DC Power was supplied by large Edison batteries charged by a motor-generator (mentioned in another thread). This system was installed in 1961 and belonged to the Enon Valley Telephone Co, later bought out by Alltel. It was scrapped in late 1987 early 1988 (yeah, it took a few weeks to remove the eight big switching frames!) and replaced by a very small box that I know nothing about.