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  • Zellweger is the brand name of an electric switching device used to control off-peak electrical loads such as water heaters. It is an example of carrier current signaling. Power stations transmit a ripple signal on the main transmission lines when off-peak rates start. This ripple noise is picked up by the Zellweger, which after a random delay turns the hot water heater on. The noise is often picked up by other equipment, especially audio amplifiers and stereos and the noise can cause problems with other electrical devices. Even some telephone lines can pick up the noise. The noise can be particularly obtrusive from some fluorescent light systems. Newer electrical meters incorporate this technology into the meter. "Time of use" meters charge electricity to the current tariff within half an hour, giving customers incentive to run appliances such as dishwashers, pool pumps and clothes dryers during the night.