From: dave@westmark.com (Dave Levenson)
Newsgroups: comp.dcom.telecom
Subject: Re: Apartment Security Stupidity
Date: 23 Jan 93 15:01:26 GMT
Organization: Westmark, Inc.
X-Submissions-To: telecom@eecs.nwu.edu
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X-Telecom-Digest: Volume 13, Issue 39, Message 1 of 12

Regarding apartment security systems, Pat writes (in part):

> [Moderator's Note: All the landlord needs is a few long distance calls
> made from that phone to demonstrate a 'regular phone line' is NOT a
> cheaper way to go. Some landlords may even be too stupid to have those
> phones blocked from 900/976/incoming calls...

Where my parents live, the entrance phone translates a two-digit
tenant number into a seven-digit POTS number, pulse-dials the number,
and allows the tenant to unlock the door by a DTMF signal.

The line is arranged for pulse-dialing only (which is why the phone
uses pulses) and the transmitter is not enabled until dialing is
complete.  There is no switchook.  Entry of the tenant-code causes
the phone to go off-hook, pulse-dial, and then enable the
transmitter.  There appears to be no opportunity to enter
tone-dialed digits, or to introduce additional pulses, or even to
get the CO dialtone, other than the obvious possibility of
physically intercepting the CO pair between the phone and the
demarc.

Tenants are encouraged to get call-waiting service, to reduce (but not
eliminate) the busy-signal problem.  The only obvious security hole
here is the call-forwarding hole, and even that is under the control
of the tenant.

If I lived there, I'd much rather have that risk than have some
strange CPE that is not under my own direct control sit between my
telephone set and my CO loop.  Wouldn't you?


Dave Levenson	 Internet: dave@westmark.com
Westmark, Inc.	 UUCP: {uunet | rutgers | att}!westmark!dave
Warren, NJ, USA	 Voice: 908 647 0900  Fax: 908 647 6857


[Moderator's Note: Well Dave, I'm not sure if I would or not. This
would be purely an applications problem, and depend on several things.
Since I keep my modems on a line totally separate from my 'voice'
line, a call-waiting signal from the door would not influence the
connection. As for a 'strange CPE that is not under your control', it
is really designed to be transparent and I think the advantages out-
weigh the disadvantages. To be sure, you cannot control the call-
waiting, even if you otherwise have it turned off with *70. You cannot
forward the calls, even if your phone is otherwise being forwarded.
You can of course unplug the phone or turn off the bell in order to
avoid the disturbance. 

On the plus side however, if you otherwise hate call-waiting and do
not want it on the line for ordiinary phone usage, you still get the
flexibility of responding to the front door without having to stay off
the phone for some period of time when visitors are expected. You can
forward phone calls while allowing visitors at the front door to leave
a message on a cheap answering machine installed just for the purpose
of picking up calls from the door. If front door calls were allowed to
be call-forwarded, there is always the risk the place to where calls
are forwarded would be busy. At least with an answering machine which
answers the door (use one of those devices which listens to the ring
and forwards to a device, i.e. fax, modem, etc to keep the answering
machine from responding to regular calls) when you are gone, people
could be given some message about 'I am busy now and can't receive
visitors'; they would not be told you were on the other side of town
somewhere and not possibly able to get home prior to them burglarizing
your place and escaping at their leisure. So, you have to define your
specific requirements to detirmine if a 'strange CPE in the line' is
the way to go or not. Overall, I prefer the stand-alone units.  PAT]