Found this discussion over at alt.electronics. Those Brits are all the rage some times. Kinda enjoyed the read and thought I would share.
We have a wireless network at work which appears to have gone downhill since the workmen installed PIRs for the burglar alarm. One of them in particular appears to cause dropped packets the closer a laptop is to it. Is this possible?? It's not a wireless PIR as far as I know, as I can see some leftover cable he was using which is a multicore (about 10 cores) type similar to phone systems, so I assume this is for the signal aswell as power. The person in that office swears blind that there were absolutely no problems until the PIR was installed above her desk, and now when I check, about 60% of the packets are being dropped. Moving her laptop to the opposite side of the room it drops only 5% of packets. PIRs used to just pick up infrared of your bodyheat, but I think now they are also motion sensors? Perhaps this means they are sending out a signal and bouncing it off you? Perhaps this could interfere with wireless networking?