GB1342206A - Clock synchronizable from alternating current and a transmitter for use therewith - Google Patents

Abstract

1342206 Electric clock systems DIEHL 22 Feb 1972 [2 March 1971 (2)] 8053/72 Heading G3T A clock comprises an electro-mechanical oscillator - tuning fork 22 Fig. 3 - which is magnetically coupled to the clock movement and time indicator. The fork oscillations are maintained and synchronized to mains frequency by amplified synchronized pulses received wirelessly from a transmitter which is electrically connected to the mains. In the event of large deviations e.g. 0À15 Hz between the synchronized pulse frequency and the tuning fork frequency, or in the event of mains failure, a drive circuit (which also acts as a synchronizing circuit) including - an oscillation amplitude regulating transistor 25, operating transistor 24, drive coil 21a and a pick-up coil 21b, takes over the drive at the natural frequency of the fork. The drive circuit is energized by a battery in the clock. The transmitter Fig.6 is an electronic module the size and form of an outlet plug and is pluggedin to a socket in the same building as or vicinity of the clock. The transmitter produces a 25 KHz carrier modulated by impulses at twice the mains frequency (i.e. at 100 Hz) from a full wave rectifier 35, a glow tube 36 passing only wave portions above a threshold voltage, e.g. above the mains R.M.S. voltage amplitude, to a ferrite antenna 34. Instead of using the glow discharge tube the rectifier bridge may include a respective Zener diode 37, in at least two arms. Thereby the modulating waveform will have sufficiently wide keying gaps between pulses as, illustrated Fig. 5 (not shown). The transmitted wave, is picked up by a ferrite rod antenna on the clock and applied to the base of a transistor 20.