Radiation relays are widely used for process control in factory production; they are used also in railway traffic signalling systems. There are two types of radiation relays. The one is cons-tantly in operation at low counting rates and gives signal on arrival of pulse of high counting rates; the operation of the other is the reverse. The former type is dealt with in this paper. It is very important that such insutruments should be highly reliable and “Fail-Safe”.
A pulse width jamming circuit has been devised. Every incoming radiation pulse is shaped to a uniform wide rectangular wave form by an electronic circuit. These shaped pulses are power amplified with transformer coupled A. C. amplifier and, after rectification, utilized as a relay power supply.
At high counting rates, overlapping of pulses deprives the rectification of its effect, hence no power to operate the relay, establishing the pulse width jamming.
As the generated power is made strong enough to operate the relay, energization of the relay at low counting rates is the evidence of normal working of the whole system. Thus, the conti-nuous Self-Checking action becomes possible.
Any failure in any part of the circuit fails to deliver real pulses or gives spurious high rate pulses, rendering the power to relay to vanish. Thus, Fail-Safe action is achieved.
Another type, the coincidence counting type, of radiation relay is outlined.
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