In the early 20th century, as telephone wires carried more messages and radio broadcasting matured, maintaining stable electrical frequencies and devising means to monitor the frequencies became critical technical problems. In 1927, Canadian-born Warren Marrison, a telecommunications engineer, was searching for reliable frequency standards at Bell Telephone Laboratories. Building on earlier work in piezoelectricity by W.G. Cady and G.W. Pierce, he developed a very large, highly accurate clock based on the regular vibrations of a quartz crystal in an electrical circuit.