TELECOM Digest OnLine - Sorted: Is This Possible? 2 Lines Squeezed Into One Line Phone??

Is This Possible? 2 Lines Squeezed Into One Line Phone??
31 Mar 2006 16:31:12 -0800

I have the need to squeeze 2 lines into one line on my phone.

[Note - getting a 2 line phone is not a solution as I already have a 2
line and 2nd line is taken by VOIP.]

One of the lines is standard tel co line -- other is essentially my
gate bell. In my fantasy -- I imagine talking on the phone and when
someone rings the gate, the call waiting feature alerts me and I can
jump back and forth. Is this possible or am I deluding myself?

[TELECOM Digest Editor's Note: You are _not_ deluding yourself. It is
quite possible, and is done frequently. I had this on my _two line_
phone (a little button near the top of the phone, twist it one way
for line one, twist it the other way for line two, raise the plunger
of the switchhook to put either line on hold). Let's talk about what
you refer to as your 'gate bell'. Are you the only user of this 'gate'
or is it a common entrance way into the building for many people?

There was a device made by telco years ago which was a sort of
hybrid centrex. In addition to your phone, and a phone at the gate,
there was equipment in the telco central office. All the pairs coming
to your building from the central office were 'dedicated'; that is,
always kept for just that purpose, serving your building. This system
was called 'Enterphone'. The front gate phone ran on a pair back to
the central office and the device where it was distributed out to the
individual apartments, by _temporarily_ camping onto the associated
pair. Now in more recent years, since telco went out of business, the
same device has been mounted at the customer premises instead and
it goes by the name _I_nterphone. Other than Enterphone versus
Interphone and the box with the electronics inside it being located on
customer premises versus at the central office, the rest of it works
the same way.

Assuming there are several users of the 'gate' then you need a larger
control box. If you are the only user, then a smaller version is quite
enough. Person at the gate wants to enter; lifts phone, gets dial tone
and dials your _code number_, NOT your telephone number. The little
electronic box hears what was dialed, and 'translates' it into the
number associated with your wire pair. Cheaper versions of this simply
translate it into your _phone number_ (and thus send it back to the
central office for handling) but there are problems with this version
which I will explain in a minute. Better quality units translate what
was dialed into your pair number locally, then look for that pair in
your own house wiring. Finding that pair, it 'tests for busy' and if
the line is not in use, it temporarily seizes the pair, inserts a
short, distinctive ring tone on it, repeating as needed three or four
times. If when it tests for busy, it finds that your line is indeed in
use, it inserts a 'distinctive call waiting tone' (different so you
can tell if the call waiting is another outside call arriving or it is
the gate calling) and presents that tone instead.

Above I said 'better' and (a bit more expesnsive) to translate the
code number dialed into your 'house pair' number rather than trans-
lating it into your telephone number and handing it back to the
central office because if you do not have call-waiting on your line
otherwise, the gate-visitor could get a busy signal when you did not
want it (now gate knows you are on the phone with someone) or if you
are not on the phone (and get a normal ring from the c.o.) you have
no way of knowing it is the gate calling, which could make a
difference. The really cheap Interphone systems just tell gate to dial
your number (?!) which is the worst of all; at the very least you want
a code number dialed (which is changeable at will) and a translation

So now you have received a gate call, how do you deal with it? The
gizmo detirmines your line is free (or was busy, but presented a call
waiting signal and allowed you to tap the hook and click in) and it
puts the central office line on hold (assuming you were on a call) and
allows you to dial '4' to accept the gate visitor or something else to
deny the gate visitor and return to the call you left on hold. If you
decide to accept the gate visitor and dial '4', the gizmo in turn
throws a current load at a solonoid which unlatches the gate for
some preset length of time (typically 4-5 seconds) allowing the person
at the gate to open it and walk in, then the solonoid clicks shut and
the gate is locked once again.

So you were partly right and partly wrong: you used the phrase
'squeeze two lines onto one' and that it does not do. A pair is only
good for one call at a time; something has to 'hold' the other call or
busy it out. But this gizmo Interphone/Enterphone sits there midst all
the house pairs, with central office pairs coming in and going out the
other side, and upon signal, examines the appropriate pair, seizes it
for a couple seconds and does its thing. With most Interphone/Enterphone
devices, they are set to time out after 'conversations' which can last
ten or twenty seconds tops. After all, how long does it take to answer
the front gate and tell the person to come in, or go away, or
whatever. I do not know who sells these devices currently, you might
ask Mike Sandman for advice, or possibly Google for
'Enterphone' and also for 'Interphone'. PAT]

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