All time distribution systems must have an accurate controlling clock. Carl August Steinheil, who first applied electricity to time distribution, used the term 'central' clock; Alexander Bain later referred to the 'parent' clock, where in England the term 'master' clock would be used for the central clock which supplies accurately controlled current pulses to the circuit of controlled or impulse dial clocks. The first master clock capable of combining both functions was devised by Steinheil in 1839, Bain's following a little later. It was not until 1895 when Frank Hope-Jones and George Bennet Bowell invented the synchronome clock, or remontoire, that electric master clocks became absolutely reliable, their clock sending out current pulses at half-minute intervals. Many other makers devised similar clocks later, but the synchronome was the most successful. Modern master clocks are of the quartz-crystal type and have electronic circuits generating the current pulses to drive the impulse dials.