[VoIP] Another WE question

[John R. Covert]

>Autovon was a 4W network

Although Autovon was a 4W network, 99.99% of Autovon calls were
placed by "users", not "subscribers".  Users did not have special
phones at all.  Autovon "users" accessed the network by dialing "8"
from the PBX or Centrex serving the military installation.  So even
though every 202 OXford x-xxxx number at the Pentagon also had the
Autovon number 22x-xxxx, not one of those phones was a four-wire
phone.

Only Autovon "subscribers" on direct Autovon lines running directly
out of the hardened Autovon switches would have been arranged for
4-wire operation.  Thus the four-wire phones were rare, and would
almost always be an additional, separate phone except in those rare
places where no PSTN access was needed (since there was no direct
PSTN access from Autovon, one always had to ask a base operator
somewhere to extend the call as a courtesy).  

I think the 3568 phones could be arranged so that the 4-wire
capability was only in effect on certain keys, so that it was
possible to have both 2-wire PBX and direct Autovon lines on
the same set in the same key system, but I never saw this done,
which is not to say that somewhere with  direct lines on a
large number of desks this was not done.

Every phone with a type 66 Autovon keypad which I ever saw was
a 3568, even if there was only a single line on the phone.  There
were a few special arrangements in tactical consoles where there
would be a type 66 keypad in the console connected to some sort
of custom arrangement.

The lines in the Autovon switch were class-marked with the
highest priority authorized for use.  The mere presence of the
"FO" button on the phone did not mean that phone could place a
call using it, since Flash Override was reserved to "(1) The
President of the United States, Secretary of Defense and Joint
Chiefs of Staff, (2) Commanders of unified and specified commands
when declaring either Defense Condition One or Air Defense
Emergency and other national authorities the President may
authorize."  It should be noted that the whole precedence system
has been redesigned and the precedences renamed.

A four-wire arranged phone still did all of its loop signalling
on a standard loop circuit which carried the transmit (from the
phone) path; this was connected to the network in the normal
manner.  The four-wire difference was that the receive path
went directly (through only surge protection) to the receiver.
I'm pretty sure the 3568 sets also had a small local side-tone
generation circuit to provide a natural feel.  Switching was
provided by specially modified No. 5 Xbar and a special version
of the No 1 ESS.

I may have located a source of 3568 sets through Google.  The
date of the blog entry I found was last December, and I'm
trying to contact the blogger.

There may have been a phone in temporary production called the
3500, but it was a 1954 cross between a model 300 and model
500.

/john