bmk@mvuxi.att.com (Bernard Mckeever) (09/13/89)
Being new to this group I never took the time to research its' history
but if what I suspect is true, the group has changed quite a bit over the
years. The group name, comp.dcom.telecom, suggests a natural evolution
from the comp {computer} hierarchy to a group interested in machine to
machine communications, comp.dcom , and further specializing in machine
to machine communications over telephone facilities.
Today we almost have usable computer to computer communications ;-}
over telephone facilities, in fact we are using it now. Thanks to T1
pipes and digital transmission circuits, relatively large amounts of
data can be moved from point A to point Z quickly and accurately. But,
and by now you may have guessed where I'm headed, It wasn't always so.
One of the early forms of "data" communications that still has a few
applications left is the telegraph. Several of the older alarm
reporting systems used by fire departments cling to this technology
because it still works, and the tariffs for telegraph grade facilities
are cheap and hard to change for political reasons. Your favorite
alarm company may still be using McCulloh systems for home and
business protection. Today several vendors have T-CXR channel units
for this service, but it is still a basic series [just like old
Christmas tree lights] circuit that causes the Telco nightmares when
the circuit goes open.
Western Union at one time had a huge telegraph network that spanned
the globe. Often telegraph circuits were transported over analog
carrier systems. I can remember the 43A carrier system that combined
up to 17 separate telegraph circuits on one N1-CXR channel [4 khz
bandwidth]. We had two systems of N1 carrier that each had 10 43A
systems on them. From time to time one or both of the systems would
fail when the A1 cable under the river started to go belly up. NY 7
Telegraph [the control office] would be on the tie line in seconds
arranging a reroute.
Other early applications of data transmission were TWX, another
Western Union service. The Bell System was also allowed "some" TWX
like service. This service used private network switches and addresses
were 10 digit numbers. This is how the now well debated 510, 610, 710,
.....etc. area codes were used. Strangely, this network was to a large
extent maintained by the Bell System and much of the equipment used to
provide the service was located in Long Lines switch rooms. Other
Common Carrier [OCC] decisions forced AT&T to cancel the contract with
W.U. and legal battles began. W.U. cut over to its' own satellite
based system several years later. TWX service ran at several speeds
depending on the model of TTY you had, TTY=Tele TYpewriter, the later
one would operate at 110 - 150 baud. What a racket that mechanical
device made at such "high speeds".
Another common data application was the dumb terminal to host
connection, used mainly with time share systems. Connections were
typically 300 baud, and the modems were much bigger than a bread box.
Connections were available in two flavors, dial-up and private line.
Well thats enough for today, time to go for now.
Bernie McKeever
508-960-6289
[Moderator's Note: TELECOM Digest began publication August 25, 1981. It
began as a break-away from HUMAN-NETS, as a place where the technical
aspects of telephony could be discussed. Jon Solomon said that it was
intended for messages not of general interest to the entire HUMAN-NETS
readership. Volume 1 Number 1 had a discussion on Dimension systems.
About the same time that divestiture occurred, more and more of the
messages began appearing in the Digest discussing telephone-related, but
non-technical topics. The early issues of the Digest were published at
Rutgers University; it changed sites on several occassions as jsol changed
jobs or his residences. Its last home was at Boston University. I moved
the Digest to Evanston, IL in February, 1989. PT]