Re: Wired or Wireless alarm systems?

[Crash Gordon® <NONE@xxxxxxxx>]

sheesh, you're MUCH worse than a nagging wife.


<-pull@shoot> wrote in message =
news:o2da61p84i0p5qe5fn8ujjveor1uskqgea@xxxxxxxxxx
>=20
> What is the basic difference between wired and wireless alarm systems?
>  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.
>=20
> So the comparison is easy, the WIRED WIRES versus a WIRELESS data link
> between sensors and the control panel.
>=20
> WIRED:
> - Each sensor has "hiss own" cabling, hiss own data transmission link.
>  All attempts to tamper sensor boxes, short or cut sensor wires are
> detected without any ambiguity an with no delay.
>=20
> - 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.
>  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.
>  This makes the system data link low frequency selective by
> attenuating the eventual High Frequencies reaching the equipment by
> huge power transmitters.
>=20
> - 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).
>=20
> 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) =3D ratio 100 000 times =
less
> power required to disturb wireless systems)
>=20
> - 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.
>  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...
>=20
> 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).
>  They "attenuate" more or less, depending on the quality of the
> receiver, the frequencies beside that privileged frequency, its called
> the bandpass attenuation range (essential quality comparison data not
> provided and published by the manufacturers in order to mask how bad
> the bandpass is).
>=20
> The sensor transmitters:
>   In wireless alarm systems the transmitting power is limited by law
> and by reasonable battery live time.
>   The RF transmitter power of the sensors is of the order of 10
> milliwatt (mW), low, very low.
>=20
> 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.
>=20
> - 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.
>=20
> 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).
> - 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.
> - Wireless alarm systems are not reliable, they can be interfered and
> disturbed/muzzled due too and by an outside transmission.
>=20
> FINAL NOTE:
> - Don't forget that in order to interfere wireless alarm systems that
> the RF disturbing signal source should satisfy some frequency
> requirements.
>  For example; cell phones with theyre 2 watt power don't satisfy that
> frequency dependent requirement and as such don't disturb normally.
>=20
> Paul
>=20
>