One of the major shortcomings of this technology was that if the television set was exposed to direct sunlight, it could inadvertently trigger one of the remote control functions.

A system based on radio waves was briefly considered but rejected because the signals could easily travel through walls and could inadvertently change the channel on a neighbor's television.

In the 1960s, Adler modified the remote control to use ultrasonic signals, a technology which went on to be used in television sets manufactured for the next 25 years, until replaced by infrared systems which could transmit more complex commands but required batteries to run.

By the time of his retirement from Zenith, officially in 1982, Adler was the company's Vice President and Director of Research.

[6][1] Robert Adler died in a Boise, Idaho, nursing home of heart failure at age 93.