Bob Dolph Answers Questions on False Alarms, Spare Pairs to Transmit Video

Q: How can I reduce passive infrared (PIR) false alarms from being caused by spiders and other small insects crawling across the sensors?
A: An old technique is to set up another PIR looking at the same detection zone and wire the contacts in parallel so that they must both trip at the same time to break the alarm loop.

Q: Can I use spare pairs in an existing telephone system to transmit video using a UTP (unshielded twisted pair) device?
A: Yes, many times this can be a nice little way to save on cabling or in a retrofit situation. Make sure to use “dry copper” pairs. There should be no dial-one or 48 volts on the pairs. Check out companies like NVT ( for UTP equipment.

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