[Asterisk-Users] far end disconnect supervision

[Lance Arbuckle]

Rich Adamson wrote:
> 
> > > > I'm starting to shop for my first channel bank and one of the features
> > > > that eveyone seems to recommend is "far end disconnect supervision".
> > > > What other terms do various manufactures use to describe this same
> > > > feature ?
> > > >
> > > > Is "calling party disconnect" the same as "far end disconnect
> > > > supervision" ?
> > >
> > > Yes, in most readers terms. However, in some cases marketing/sales
> > > people may have written stuff with no clue what they are talking
> > > about.
> >
> >
> > Is "far end disconnect supervision" BOTH a service/feature/line
> > signaling provided by the Telco AND a feature of some channel banks ?
> >
> > If some channel banks don't support this, how on earth do they know when
> > the telco side of the call has hung up ?
> 
> If you go way back in history, channel banks were only used by telcos and
> at least initially were only required to pass signaling between central
> office switches. It wasn't until fx cards were added that channel banks
> had to be concerned with "calling" and "called" party disconnects. In some
> states, the regulatory agencies governed what could (or could not) be
> deployed and under what conditions. "Called party disconnect" was frequently
> used by court order for police verification on certain calls, while
> "calling party disconnect" was the norm. At that time, customer lines were
> directly connected to the central office switch, and it was functions within
> the switch that controlled calling/called party disconnects.
> 
> If the telco deployed a channel bank with fx-type customer interfaces, the
> channel bank would need to support "calling and called party disconnect" in
> order to inform the central office switch of call status.
> 
> If the telco deployed a channel bank with interfaces to a customer's pbx
> where signaling used tones (as an example), the channel bank would not
> need the added electronics to support disconnect supervision.
> 
> Disconnect supervision refers to opening/closing the 2-wire circuit (as in
> hanging up a telephone), and in some cases, reversing tip/ring (48 volt
> polarity change).
> 
> (There are a number of other interfaces available for channel banks beside
> those designed for two-wire fx's.)
> 
> Since there are lots of old (and new) channel banks being sold on ebay, etc,
> that may have been designed for different purposes, some will support
> disconnect supervision while others do not, some are two-wire while others
> are four-wire, some support E & M signaling (extra wires per channel), some
> supply 100vac ringing voltage while others do not, some run on only 48 volt
> DC power while others are 110 vac power, etc.
> 
> If you're looking for a channel bank to interface phones with asterisk, then
> keywords would include "2-wire", "disconnect supervision", "fx lines", etc.
> Might also ensure it can supply the needed 100 vac ringing voltage
> (historically referred to as a ring generator).


Yes, I'm looking for a channel bank to interface analog phones and pstn
lines to asterisk.  I've got a simple test system setup with the TDM10B
and X100p and want to continue learning asterisk with the T1 card.

I've been reading the list archives and searching Ebay for channel
banks.  There are lots of Carrier Access Corp (CAC) Access Bank I and
II's available but I don't explicitly see anything about "calling party
disconnect" in the user manuals.  The CAC Adit 600 manual, on the other
hand, states that "calling party disconnect" is supported on the FXO
interfaces.  That's great, but I haven't seen any on Ebay and I can't
justify the expense of a new unit.  Acording to the list archives the
Adtran 750/850 units work well but I haven't read the manuals for those
units yet.

Basically, I was hoping to purchase a functional, used, older channel
bank for a few hundred dollars so that I could continue learning
Asterisk and to also have a system to demonstrate to potential clients. 
Any suggestions welcome.....

-Lance