Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!mailrus!accuvax.nwu.edu!nucsrl!telecom-request
From: wb8foz@mthvax.cs.miami.edu (David Lesher)
Newsgroups: comp.dcom.telecom
Subject: Re: Call Forwarding Set From a Remote Site?
Message-ID: <12339@accuvax.nwu.edu>
Date: 19 Sep 90 02:05:27 GMT
Sender: news@accuvax.nwu.edu
Reply-To: David Lesher <wb8foz@mthvax.cs.miami.edu>
Organization: NRK Clinic for habitual NetNews abusers
Lines: 56
Approved: Telecom@eecs.nwu.edu
X-Submissions-To: telecom@eecs.nwu.edu
X-Administrivia-To: telecom-request@eecs.nwu.edu
X-Telecom-Digest: Volume 10, Issue 658, Message 4 of 8


|I haven't seen a device that will do this, but it isn't that tough to
|design.  You could program your Watson or other voice mail board to do
|it for you.  The major problem is how do you dial into the device to
|change the programming, if it's already forwarded and you only have
|one phone line at home?

|Answer: Have the thing unforward for a short period if it receives N
|calls in quick succession.  

I've looked at another method (call it Hal), but have not spent much
time on it.

Don't use call-forwarding. Rather, use 3-way calling. 

Set up autoanswer with TT decoder driving Hal driving TT encoder.  You
call it up. Hal answers. You feed it a password, and a desired number.
It flashes the line, grabs the 2nd {logical, not physical} 'pair',
dials the number, flashes again. You hear ringing, answer, talk, etc.

Problems we've thought of so far:

Supervision/timeout: How do you assure that Hal will not get hung?
Possible solutions: CTCSS (a subaudible tone encode/decode scheme used
in the two way radio business.  Also called PL -- the Galvin Mfg.
trademark. While frequencies around 100 hz. are used there, something
above 3000 might be more usable in this application.  When Hal hears
no tone for 1 minute, he goes back on hook until rerung. If a ring
counter reaches 15 rings, hardware counter reboots Hal.

Security: Write the software so he CANNOT dial anything other than
seven digits. (Unit is to be located in a state with a PUC-mandated
"if it's toll, it's gotta have a '1' first rule" so any call would be
local. Flat rate service is the norm. Thus, if the software is intact,
no abuser, even with passwords, could do anything but tie up Hal.
Note the the incoming call has NO way to directly dial the outgoing
number -- Hal must. (Oh, yes, 976 blocking is there, too ;-])  Be
extra-sure: order the line with no default carrier.

Sequence: Will that CO allow the second flash (to tie the ends
together) before getting supervision from the call Hal dialed? (Some
do, others don't) If not, how do you identify that the far end has
answered, was busy, etc? Even if you do, how do you convince the
called party to hang on until you get connected? (i.e. "Please stand
by for an important call.")

One important advantage to this method is that Hal could automatically
forward 'incoming' calls with no touchtones (within x seconds) to the
'control' house. This gives you automatic incoming service from the
distant town, too.

Net-comments?


wb8foz@mthvax.cs.miami.edu   (305) 255-RTFM
pob 570-335   33257-0335