Front view of the five-bay equipment cabinet of the ammonia atomic clock built by LSRH and Oscilloquartz for the 1958 Brussels World’s Fair.
Thirty-one leader lines identify its components. The left-hand bay contains the ammonia supply and fore-vacuum equipment: the ammonia cylinder (1), rotary-vane forepump (2), fore-vacuum valves (3), NH₃ inlet to the high-vacuum vessel (4), and ammonia purification apparatus (5). The central bays contain the high-voltage generator (6), mains-voltage monitoring instruments (7), high-vacuum gauge (8), high-vacuum vessels housing the beam nozzles and focusing systems (9), cavity resonators (10), and the rectifier supplying their heaters (11). The microwave receiving equipment includes its power supplies (12, 15, 21, 25, and 26), cathode-ray oscillograph (13), microwave section (14), and intermediate-frequency amplifier (24). The frequency-comparison and checking equipment comprises a counter (16), 8,500.756 kHz auxiliary oscillator (17) and its thermostat unit (20), frequency multiplier (18), 100 kHz–8,500.756 kHz comparator (19), radio receiver for checking against time signals (22), and distribution panel with a connection for the quartz clock (23). The lower part of the cabinet contains the main switch (27), main switchboard (28), diffusion-pump water-cooling monitor (29), electronic mains-voltage stabiliser (30), and diffusion-pump compartment (31).