Yeah, automatic doors are generally infra-red or ultrasonic though some of them can spew out a bunch of nasty EMF. Cable tracing probes are not only good at pi

Yeah, automatic doors are generally infra-red or ultrasonic though some of them can spew out a bunch of nasty EMF. Cable tracing probes are not only good at picking up signals from the trace transmitter, they also amplify other types of EMF. You can hear a ton of noise from a keyboard as it goes through the scan loops. LCDs squeal at their refresh frequency. Automatic door detectors make a ton of noise too. I'm not sure how close you'd have to be to the detector you'd have to be, but if the resonant frequency matched and you're tall enough to nearly make contact maybe it's a factor here.