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Posted by T on October 1, 2007, 5:10 pm
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nospam.kd1s@cox.nospam.net says...
> Date: 30 Sep 2007 11:45:29 -0400
> To: telpost@iecc.com
> Subject: Re: Analog Cell Phones
> Organization: The Ace Tomato and Cement Company
> User-Agent: MicroPlanet-Gravity/2.60.2060
>
> says...
> > >Gray, Charles wrote:
> > >
> > >> The alarm industry still makes use of AMPS cell phone systems for
> > >> connectivity from their client=3Fs premises. In March 2006 an Alarm
> > >> Industry Communications Committee petitioned the FCC to extend the AMPS
> > >> =3Fsunset=3F date by two years to February 2010. They asserted that
there
> > >> were more than a million analog alarm radios and they say that there
> > >> just isn=3Ft enough time to change all of them out by February 2008.
> > >> Never mind that they have already had several years to change their
> > >> equipment. One of my =3Fmottos=3F is: Lack of planning on your part
does
> > >> not constitute an emergency on my part.
> > >>
> > >>
> > >
> > >The alarm industry seems to always be behind the power curve. Some of
> > >them still use dial pulse instead of DTMF for wireline dialing.
> > >
> >
> > It wasn't all that many years ago that the phone companies charged a
> > premium for DTMF dialing, which adds up over time.
> >
> > For an automated application, using DTMF may speed up your dialing by
> > a few seconds, which really dosen't matter in the end.
> >
> > I recall that one of the other arguments that the alarm industry used
> > was that the manufacturers had been very slow in making replacement
> > products available, and that replacement equipment was still in short
> > supply. In other words, they could not do upgrades because the equipment
> > was not available.
> >
> >
> >
>
> One of the really interesting aspects of alarm systems it seems many of
> them use the Z80 CPU. I still remember some of the opcodes for that
> processor.
>
>
> ***** Moderator's Note *****
>
> My first "real" computer was a Heath H89, which also had a Z-80
> processor. IIRC, it had a nice "area move" capability that the 8080
> didn't, allowing a programmer to move blocks of memory around with a
> single command instead of by calling a subrouting to iterate through
> the memory range.
You are correct abbout the block move capability. My first system was a
TRS-80 and the video was from 3C00 to 3FFF in RAM so it was easy to swap
out pages even on that rudimentary graphics system.
> I was running CP/M, and I had to modify it so that it would send EBCD
> code to an Anderson-Jacobson 841 printer, which I had bought at the
> M.I.T. surplus store: the machine was a Selectric typewriter, with
> solenoids on the bottom of the mechanism to allow the (RTL)
> electronics to drive it.
>
> The AJ-841 used EBCD code, which is not the same as EBCDIC: it's a
> six-level code, which means that there are only 64 posible bit
> combinations, so it includes "shift" and "unshift" characters, just
> like Baudot. Using the shift/unshift combination gave 126 possible
> codes, which was enough for most use.
> Ah, the good old days.
Oh my, fun and games on that one. I pretty much knew what was on the
expansion card edge on my system and used it for various project. But a
friend modified the hell out of a Model III, it had quad serial ports
and we re-wrote TRS-DOS to do ISAM file systems.
| ![Re: Analog Cell Phones]](/images/header.jpg)
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