This item is a program timer that was used in conjunction with the Synchronome clock, which is placed above this timer in the Physics Museum, to control the bells in the Parnell Building from 1955. The master clock was made in Brisbane by the Synchronome Co. of Australasia but they imported this timer from the Synchronome Co in England in 1955.
The Synchronome Electrical Company of Australasia was founded by Alfred George Jackson in Brisbane in 1904. The company built and imported clocks that used the Synchronome electrical timekeeping system that Frank Hope-Jones and George Bowell developed in England in 1895.
Bells were rung at five minutes to the hour to mark the end of one lecture and again at five minutes past to mark the beginning of the next. This unit uses a heavier movement than the normal slave clocks, however it has twin coils and a double locking system that would have been used in early slave clocks. When the electromagnet receives the electric signal from the master clock it activates a pawl which drives a large brass wheel with holes into which pins can be inserted. The wheel operates three sets of contacts. A second wheel is used to restrict the bell to ringing on certain days. This program timer is set to ring on Monday, Tuesday, Thursday and Friday only.
The duration of the bell ring was controlled by a mercury timer. The mercury timer was tripped by a separate relay, which energised the mercury switch coil every 30 seconds. Once the switch was energised the cams and switches of the main movement tilted the vial of mercury 45 degrees clockwise. This allowed the mercury to cover two contacts in the chamber on the right, completing the circuit. At the same time the mercury would start draining through a narrow neck into a chamber on the left. After about 10 seconds the mercury would be drained to the point where it would no longer cover the contacts and the circuit would be broken, stopping the ringing. The mercury vial was then returned to its initial position for the next bell ring. When the mercury vial is returned to its original position, the mercury flows through an alternative tube so that it does not cover the contacts.
The program timer also has a switchboard, located at the bottom of the case below the movement. The switchboard can allocate different electric signals to different circuits, controlling which bells rang and when. A similar device was used to control experiments at the ionospheric research field station at Moggill.
This item is part of the UQ Physics Museum Electric Clocks Tour
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