Electrophotographic copier

An alternating power supply for a copier fuser is sensed for zero crossings by detector (40), which steps counter (39). At the end of an apparatus cycle, the count in counter (39) gates latch (31) to store a new temperature reading from the fuser, according to a digital code (D). Stepping of the counter causes a stored predetermined sequence of numbers (B) to be fed, one at a time, from store (35 or 36) to comparator (32). If the comparator determines B >/= D, it causes a triac in the fuser circuit to pass the current half-cycle pulse from the power supply. The stored predetermined sequence of numbers is chosen so that the number of pulses generated per cycle varies inversely with the magnitude of the fuser temperature (D), for maintaining the fuser temperature constant.