Your fanciful imagining are far removed from real life as lived by most of us. So tell us, Bernie, what is your estimate of the probability that, in an ordinary domestic house in an ordinary residential street, interference will block the signal from a sensor at the same fraction of a second that a burglar breaks into your home?
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You know the probability depends on what electronic equipment is being operated in the area. A baby monitor transmitting at 10% occupancy of the channel will mean on average 1 in every 10 transmissions could be compromised. Two baby monitors could result in 1 in 5 alarm messages being compromised if they use test before transmit protocols.
Some baby monitors transmit for more than 10% of the time and have higher ERP ( Effective Radiated Power ) than is legal. I am sure anyone with an open mind can realise what effect that will have on other equioment using the channel.
so your estimate of the probability that, in an ordinary domestic house in an ordinary residential street, interference will block the signal from a sensor at the same fraction of a second that a burglar breaks into your home, is what?
One in five?
So by your reckoning, in one out of five times when the occupier comes home and opens his front door, the count-down will not start, and in one in five occasions when the householder sets or unsets his alarm, the signal will fail to work? And in one in five cases where a householder opens a door set to chime, it won't?
Rubbish.
One in five?
So by your reckoning, in one out of five times when the occupier comes home and opens his front door, the count-down will not start, and in one in five occasions when the householder sets or unsets his alarm, the signal will fail to work? And in one in five cases where a householder opens a door set to chime, it won't?
Rubbish.
Read what I wrote. Did you miss the bit about a baby monitor ?.
Just to make if clear for you.....If there is no other equipment nearby that emits radio frequency energy then the alarm is almost certainly going to work.
If you want to be certain the alarm will continue to work then you have to ensure there will be no systems producing radio frequency energy that affects the receivers in the alarm system.
Just to make if clear for you.....If there is no other equipment nearby that emits radio frequency energy then the alarm is almost certainly going to work.
If you want to be certain the alarm will continue to work then you have to ensure there will be no systems producing radio frequency energy that affects the receivers in the alarm system.
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M
mdf290
We did some calculations in another thread Bernard whereby you acknowledged that the stronger signal will get through.
It was then established that a signal aimed at deliberately blocking or jamming would have to be 40 times stronger or more than the signals sent by the sensors due to the inverse square? relationship of signals and distance.
Here is another question for your and all it requires is a yes or no answer.
Given that you claim Licence exempt frequencies are at danger of inteference.
Is it also true that there is nothing at all stopping someone so minded from jamming the licenced frequency?
After all a professional burglar is hardly going to say . . ooh I better not jam this signal I don't have a licence is he?
You are mis-quoting. If the distance from sensor to siren and the distance from blocking TX to siren are equal then the effect will occur when ERPs are equal. If there is a wall between sensor and siren this will reduce the signal from the sensor.
One word answer. Yes,
It is equally simple to jam a licenced radio channel as it is to jam a licence exempt channel.
Hence the reason to use wired and not wireless for critical systems of fixed items.
Hence the reason that systems that have no option but to use wireless due to one or more items being mobile will adopt counter measures such as automatic channel changing and compelled signalling protocols.
But you must also consider that licenced channels are allocated to the users in a way that aims to avoid adjacent users having the same frequency. Blocking and / or jamming will be investigated by the licencing authority and action taken if necessary.
You must also accept that the terms of the use of licence exempt channels require that equipment is tolerant of interference from other users of the channel. Blocking or jamming may be investigated but no action can be taken unless non compliant equipment is found to be transmitting.
Anyone can buy a compliant licence exempt transmitter and use it anywhere they want to. They can also buy non compliant transmitters that are higher power, one of these items is specifically aimed and sold as a jammer.
If he jams a licence exempt channel with a compliant licence exempt transmitter he is not committing an offence unless intent to jam for an unlawful purpose can be proved. If he jams a licenced channel he is commiting an offence under the Wireless Telegraphy Act, an old law but with very sharp teeth when offences occur. Forced entry to the private property where the transmitter is operating is one of those teeth.
A previously reliable telemetry link, 433.92 Mhz point to point failed due to transmissions which appear to coming from a domestic wireless headphone system.
Ask before you make statements based on your biased guesswork.
I was asked to look into why the telemetry was failing with very high error rates. An off air monitor found what appeared to be digitised audio on 433.92 Mhz.
The telemetry link sends a packet with a check sum. The packet has to be acknowledged, if there is any error which the receiving end cannot correct then the acknowledgement indicates the error and the package is re-transmitted. As you know a Yale system that is one way could not do that and corrupted packets ( alarm messages ) would be lost. Alarms using two way comms would continue to send alarm messages until one was received and acknowledged by the panel.
Just to be clear.
At each end of the link using test equipment I verified that the transmitted data ( received OFF air ) was the same as the data fed to the transmitter.
Using a borrowed signal strength meter I verified the signal in the area of the receivers was more than adequate.
That was during the day while the link was error free.
One evening when the error count was high an off air recording was made and that had the digitised audio signal concurrent with the periods of high error counts. No signal strength test were made at that time.
At each end of the link using test equipment I verified that the transmitted data ( received OFF air ) was the same as the data fed to the transmitter.
Using a borrowed signal strength meter I verified the signal in the area of the receivers was more than adequate.
That was during the day while the link was error free.
One evening when the error count was high an off air recording was made and that had the digitised audio signal concurrent with the periods of high error counts. No signal strength test were made at that time.
M
mdf290
In the case of a Premium alarm the control panel is within the home and thus meaning the sensors have a better signal path than an external TX.
YES
You appear to be not very good at gathering from words. How could I possible compare the data into the transmitter with the data it transmitted unless I was there on site with a dual trace oscilloscope.
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