In Reply to: TRAFFIC LIGHTS frequency posted by Ben-WA on June 26, 2000 at 00:06:28:
: i notice my radar detector now goes off at every intersection. the signal changes with the light. i know this is to allow the police/fire to change the light. it would be pretty cool to be able to do that, not that i would. wondering how.
I am not familiar with that phenomena but check the web site: "www.tomar.com" to view optically triggered traffic pre-emption emmiters. They market and sell a handheld traffic signal pre-emption testing device that resembles a handheld spotlight. This is however a restricted item,(for government purchase only), that they WILL NOT sell to individuals.
3M Traffic Products also has produced the "opticom" pre-emption devices for about 20 years. Some agencies still use the old tone encoders (Plectron / Butler National Corp.) to activate traffic signals and some municipalities are hard wired through the dispatch center. Early units were liquid cooled. New ones are not. Most often times they are wired to cancel when the vehicle is placed in park or when the air brakes are set.
Perhaps there is a municipal electronic services tech in the audience that can enlghten us further ?