Re: Napco MA3000 - Dialer Test on both Lines?

["Robert L Bass" <robertlbass@xxxxxxxxxxx>]

"Nomen Nescio" <nobody@xxxxxxxxx> wrote in message
news:d3d8338d4df4f17fdd6ca13aa9d586f4@xxxxxxxxxxxx
> Bass said:
>
>>> But suppose line 2 is bad?
>>
>>Have you forgotten what I said earlier about running a third relay to
>>preven
>>shorting line 1 if there is a pre-existing trouble condition?
>>
>>> More importantly, if line 2 really is
>>> inoperative and you short out line 1...
>>
>>See above.  It really helps if you know the panel before evaluating
>>someone
>>else's methods.
>
> Oh, I didn't forget.  However, it appears that you do not understand why
> the code was changed to require transmission of test signals over both
> lines, instead of just depending on the telephone line monitors.
>
> Commercial fire alarm communicators have always required two phone lines
> and telephone line monitors.  This has been a requirement since they were
> first introduced in the early 1980s.   Back in those days, when the phone
> company disconnected a phone number, it often meant someone physically
> disconnected wires at the telco central office.  That would trip the phone
> line monitor in the fire alarm panel, annunciate the trouble, and transmit
> a trouble signal over the other phone line.
>
> Today, telephone numbers are often disconnected via software, rather than
> by disconnecting wires.  This means the phone line still has voltage on
> it,
> but cannot draw dial tone.  The phone line monitor doesn't detect this
> problem.

Having been installing and servicing alarms since before the 1980's, I'm
well aware of the above.  I explained how I accomplished the job several
years ago -- prior to any changes -- using the panel which the OP described.

> So, consider a fire alarm panel set up as you propose...

Nope.  You need to consider the thread in context.  The discussion was about
a Napco MA3000.  The panel doesn't have an intrinsic function to test both
lines.  If the OP is doing a new installation, he'll likely need to use a
different product.

> Somehow, line 2 gets turned off, but without
> loss of voltage...

If the client is using Verizon, it's even worse than that.  They not only
leave voltage but also dial tone on disconnected lines.  Calls to 911 will
go through (not our issue) but calls to a C-station receiver will be met
with a message suggesting the client call Verizon to get the service turned
on.

> Perhaps the customer cancelled a phone number
> he did not recognize, or perhaps the phone company
> turned off the wrong line...

Either way, it happens all the time.

> Test time arrives, and your relay shorts out
> line 1.  Since the panel hasn't detected a phone
> line trouble, your trouble relay does not prevent
> this from happening.

You really need to read what I said more carefully.  Shorting or opening
line 1 is not done to cause a line trouble report.  It is done to ensure
that the signal from a 24-hour zone is sent via line 2.

> The panel tries to dial out on line 1 and fails.

Actually, the panel picks up line 1, finds no dial tome and goes to line 2.

> The panel then tries to dial out on line 2
> and fails...

If line 2 is bad, yes.  This will disclose to the customer that line 2 is
bad because the panel will then go into trouble.  If the C-station is
expecting the test within a certain time period they will also notify the
installer.  That is the reason for testing an alarm system -- to discover if
something is wrong *before* there's a fire.

> The panel alternates between these two lines
> until the maximum number of dialing attempts
> is reached, or until your phone line shorting
> relay times out and releases line 1.

If it is programmed to function that way, yes.  BTW, Napco can be programmed
to only send tests via a specific phone number or via both.  Nice panel.
You can program the number of tries, too.

However, once the system goes into a trouble mode, if a third relay is in
use as detailed earlier, the system will allow all succeeding calls to pass
on line 1.  I mentioned that as an option though I haven't actually employed
it.

> During the time line 1 is intentionally shorted,
> the fire alarm panel will be unable to transmit
> an alarm signal...

Properly configured, that will be about 30 seconds.  However, if the third
relay (or even a fourth) is set up to defeat the line short/cut, an alarm
event will go out immediately.  There are dozens of ways to modify this *if*
you knw the panel.

--

Regards,
Robert L Bass

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