Re: Purchasing a Home Alarm

["Frank Olson" <feolson@xxxxxxxxxx>]

<-pull@shoot> wrote in message
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>
> What is the basic difference between wired and wireless alarm systems?

Good question.  Let's review.


> It boils down to the "connections link" between sensors and control
> panel of both systems, besides that sensor data connection link both
> systems are alike.

It boils down to this.  On a wired system, a cable connects the speakers in
your headphones to a jack located on the front panel of your stereo system.
The impotant thing here is to ensure the headphone jack and the jack on your
stereo system are of a similar size.  Loose jacks can cause all sorts of
problems.  For instance, the data link between the the amplifier and your
head could become disturbed causing signal loss.  You may have to crank up
the volume so you can hear "Abba" better.


>
> So the comparison is easy, the WIRED WIRES versus a WIRELESS data link
> between sensors and the control panel.


I almost always use "wired wires" for wiring.  Unless, of course, I'm using
wireless wires in which case the only thing I'd bring in from the van would
be my ladder.


>
> WIRED:
> - Each sensor has "hiss own" cabling, hiss own data transmission link.

True.  but if the connections aren't tight, "hiss"ing may result.  Should
this occur, it's best to change the batteries on your smoke alarms, then try
again.


> All attempts to tamper sensor boxes, short or cut sensor wires are
> detected without any ambiguity an with no delay.

Not necessarily so.  For instance, if you were to leave out the end-of-line
resistors, your wired wires wouldn't sense your shorts unless of course they
were "Fruit of the Loom", in which case leaving them completely ungrounded
wouldn't be a good idea.


>
> - At a first glance the wired links are of the non-frequency selective
> type and as such are more prone to capture a greater Radio Frequency
> (RF) spectrum range of signals.

In Canada, we always let captured signals go.  In fact, I find the Judges at
the CRTC to be much too lenient regarding the spectrum range of signals.  I
don't think that a suspended sentence is an appropriate punishment for
non-frequency selective types.  And their parol eligibility is ludicrous in
the extreme.


> The data transmitted on sensor wired lines are of the low frequency
> type and as such can easily be filtered at all inputs entering the
> control panel.

Not all data transmitted on sensor wired lines are of a "low character".  In
fact some fairly ooze class and distinction.  It is for this reason that the
RF Spectrum is divided into "high brow", and "low brow", with the
"Neanderthal" being the accepted unit of measure.


> This makes the system data link low frequency selective by
> attenuating the eventual High Frequencies reaching the equipment by
> huge power transmitters.

My power transmitter is fairly average, actually.  For "huge" you'd have to
go to Texas.  In Texas they have several different types of transmitters.
There's the "short horn" and the "long horn".  Long horn frequencies are
practically inaudible unless of course you're using Monster (TM) cables.


>
> - The level of the transmitted signals on the wired lines are around
> "2Volt" to switch from on to off (to be more precise, 400mV
> interference free immunity for TTL circuits).

TTL circuits are only used with "long horn" transmitters to enhance the
audible experience.  In many cases the circuits are powder coated with
Viagra to ensure embedded objects remain fully verticle and the coils fit
snugly over them.  A small dab of silicon gel ensures proper lubrication
during insertion and withdrawl.  In many instances over 800mV can be
achieved immediately prior to the point of signal injection.


>
> WIRELESS:
> - All the sensor data is vehicle via ONE wireless data link composed
> of a low power transmitter in the sensors and a sensitive receiver at
> the input who has around 4 microvolt input sensitivity (wired 400
> millivolt (mV) / wireless 4 microvolt (uV) = ratio 100 000 times less
> power required to disturb wireless systems)

Not necessarily so.  Some low brow transmitters are mounted remote from the
sensors.  It is usually suggested that less sensitive receivers be employed
in this instance and that people with small dogs don't allow them to witness
the actual mounting process.  400mV applied to a headphone would be enough
to startle most small poodles.


>
> - The wireless data link contains all the information required to have
> a reliable connection as long as there are no other transmissions
> present who block the data communication.

Also ensure you change your transmission oil at least every 20,000 miles
(25,000 kms).  Topping up your fluids should guarantee nominal performance
with very little signal loss.


> The wireless RF receiver collect in normal circumstances the data and
> decode it. This data contains an ID (rolling code), alarm, tamper
> attempt, battery low and more information. When the signal is
> disturbed, EVERYTHING is, ID can't be recognized...

Unless of course a photo is attached.  Please ensure photographs of every
transmitter is available for when recognition becomes a problem.


>
> The receiver:
>  The receiver is made as much as possible frequency selective and
> sensitive at signals on the frequency in order to capture the week
> signals emanating from the sensors (see below).

Most wide receivers are in fact very selective as to which frequency they
catch.  CD players sending weekly signals are usually not asked to leave the
bench, but in an emergency Gatorade has been known to be helpful in
strengthening calls.


> They "attenuate" more or less, depending on the quality of the
> receiver, the frequencies beside that privileged frequency, its called
> the band-pass attenuation range (essential quality comparison data not
> provided and published by the manufacturers in order to mask how bad
> the bandpass is).

Most bands tend to pass by.  Those that don't, usually march in place until
someone moves the elephant (or the Governor's car).


>
> The sensor transmitters:
>  In wireless alarm systems the transmitting power is limited by law
> and by reasonable battery live time.

It's also speed regulated.  In most cities the maximum transit speed is 30
mph, however in some places this has been known to be much higher.  Higher
transit speeds means less transients will leave their shopping carts in
traffic.


>  The RF transmitter power of the sensors is of the order of 10
> milliWatt (mW), low, very low.


>
> COMPARISON:
> - The receive end is 100,000 times more sensitive to signals in
> wireless versus wired (4uV / 400mV);
> The ratio is even higher because the high frequencies, where
> disturbing transmissions occurs, are attenuated by low pass filters at
> the input of the wired lines.

Not if you use "high bypass turbofan" filters.  In this instance the
transmissions are less prone to interference from wake vortices, which
decreases their attenuation span.


>
> - The link in wired systems are wires who can be filtered/shielded
> against RF interferences (and by location of the wires); in wireless
> it is the open air reachable by everybody, no shielding possible.

Except for magic missle shielding.  Using mithral armored cable is also an
excellent way of protecting you from trolls.


>
> CONCLUSION:
> - An external RF transmitter can disturb both systems but the power
> required to do this is much higher in wired systems (>100,000 times).

Power is reduced when the homeowner uses the Force.  Only skilled and well
trained alarm installers should use "the Schwarz" and then only as a last
resort.  Every attempt should be made to remove the jam from the transmitter
before applying the peanut butter (or Nutella).


> - In wireless systems, the power required to interfere and disturb the
> system is similar to the sensor power (10mW) when generated at the
> same distance, RFI power should be increased if the distance is
> increased.

But if the distance is decreased, the RFI becomes DFO and all our fish
stocks are endangered.


> - Wireless alarm systems are not reliable, they can be interfered and
> disturbed/muzzled due too and by an outside transmission.

Wireless alarm systems cannot be muzzled by GM transmissions.  Fords and
Jugos are by far the worst culprits.


>
> FINAL NOTE:
> - Don't forget that in order to interfere wireless alarm systems that
> the RF disturbing signal source should satisfy some frequency
> requirements.

Unless of course your chocolate craving has been satisfied.


> For example; cell phones with theyre 2 watt power don't satisfy that
> frequency dependent requirement and as such don't disturb normally.

For those with disturbing cell phones, we suggest downloading some more ring
tones.  I quite enjoy the Imperial March whenever the office calls.  The
Darth Vader helmet also enhances the CRF (Customer Recognition Factor) and ,
oddly enough, has reduced the number of service calls I have to go out on.