[VoIP] Another WE question

[Lucky 225]

Well I had seen a '3500' on ebay once, didn't say anything about it being 4
wire, though I'm sure it was, I'm sure converting one wouldn't be to hard.
A 1500 set would be interesting though without the * or # keys lol

On 3/16/07, Steph Kerman <stfkerman at jps.net> wrote:
>
>
>
> John R. Covert wrote:
> >> 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).
> The purpose of support for mixed 2W/4W operation on 3568 sets was
> ostensibly to allow 2W PBX EXTs or PSTN lines as well as 4W Autovon
> lines on the same set.  I don't know to what extent the feature was used.
> > 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,
> Definitely was included in the design.
> > 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.
> There must have been 3504 sets in use somewhere since they show up on
> eBay.  The three 608 cord positions at one Navy base I know of had
> 66-type dials added on the keyshelves.  The cord boards were connected
> to a large 701B Centrex with "PBX Access Lines"...  4W trunks into the
> nearest Autovon switch that were accessed on a 2W basis from 701B EXTs.
>
> The PBX also had Preempt Tone supplies in the tone plant.  I saw this at
> two 701Bs which had PBX Access Lines.  I believe they were associated
> with the Access Lines.  Since there were no DTMF receivers in either
> installation that would have been capable of recognizing 4th column
> tones, I'm inclined to think that the Preempt feature was invoked
> towards the PBX from the Autovon switch.
> > <snip>
> >
> > 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.
> The sidetone path was part of the line interface circuit in the Key
> Service Unit, not part of the phone.  It also included a line amplifier
> with low Z output to allow multiple telephones to be driven without
> reduction of receive level.  However 3568 sets contain a crystal can
> relay to transfer the receiver between the internal speech network and
> receive pair depending on whether a 2W or 4W PU key is pressed.
>
> Steph
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