TELECOM Digest OnLine - Sorted: Re: Hookflash and Ground Start Analog CO Trunks From PABX

Re: Hookflash and Ground Start Analog CO Trunks From PABX

Robert Bonomi (
Fri, 04 Mar 2005 16:50:27 -0000

In article <>, Ken Abrams
<k_abrams@[REMOVETHIS]> wrote:

> A flash was (and still is, I believe) never intended to be passed from one
> switch to another. It is a means for the subscriber (phone) to signal the
> nearest switch in the chain.

> It appears that your equipment can serve either as a switch (PBX) or
> as (dumb) terminal equipment (CENTREX). When a CO termination is
> ground start, that makes it a trunk between two switches and by design
> will not pass a flash. When it is loop start, it is a line and will
> pass the flash.

> The difference between a PBX "trunk" and a Centrex "line" is not just
> one of terminology. There are technical design differences between
> the two. This was true when there was only one supplier for the
> network and a lot of these standards carried well beyond the date of
> deregulation. The fact that they offered you a solution by changing
> cards probably means that this "standard" has been corrupted.

> One final thought: At the CO end, a ground start PBX trunk originally
> was not capable of recognizing a momentary open as a flash. Thus, any
> momentary open exceeding 20 ms (or so) would effect a disconnect.
> That might still be true.

> Has the LEC really offered to provide you ground start Centrex lines?
> At one time those were mutually exclusive.

> [TELECOM Digest Editor's Note: Actually, on my PBXtra, which goes
> under the brand name 'Total Com' and is manufactured by ACNC at the
> phone number 630-241-2800, (but distributed by Mike Sandman through
> his online catalog [and he is a good friend of the
> Digest and well trusted on the net]) you _can_ pass along a hookflash
> to the next switch down the line, i.e. the central office.

Do you even understand the difference between a _POTS_ (analog "loop
start") line, and a "ground start" (aka "wink start") *trunk* line?

Does your "Total Com" connect to the C.O. with POTS lines?

If so, the fact that "flash" works with _your_ system it totally
irrelevant to the question of passing flash on a C.O. "ground start"
*TRUNK* line.

[[.. balance of 'ignorance in action' snipped ..]]

[TELECOM Digest Editor's Note: It is always so pleasant to receive
your replies, since you phrase them in such a congenial way, and
pepper them in your own, sort of special way. I think I know the
difference between loop start and ground start lines. On older, ground
start payphones for example, a coin deposited would trigger a metal
'finger' like thing which would apply ground to the line. Children
used to stick a pin in the handset cord of a payphone to get the
same results.

The TotalCom Pbxtra device connects to whatever it connects to (mine
does have a POTS line (dial 9+), an VOIP line (dial 8+) and a Cingular
Wireless cell phone (dial 7+) and other 'local' extensions (dial 100
through 104.) All I said was flashing during a call, then dialing *6
causes a hookflash to be sent back to whatever switch is next in
line. It does it through software, I think. You can also program the
entire system (as opposed to individual stations) to have *5 apply
ground. I do not know how to install that program; I have never
studied it. The various system-wide programs it is capable of doing
are accomplished by shorting two pins on the RS-232 connector on the
bottom, then using the station plugged into the zero port to dial in
the desired program codes. By itself, the PBXtra can do _nothing_; the
entire unit has to be programmed from the zero port with a jumper
attached through the RS-232 port, much as we used to program the old
Motorola 'brick phones' by reversing two leads on the battery
connector. PAT]

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