Dekatrons and electro-mechanical registers operated by transistors

In nucleonic work a common requirement is the counting of pulses occurring at relatively long intervals of 250 microsec or more. Cold-cathode decade tubes (e.g. Dekatrons) and electro-mechanical registers have proved their value in this field, but their performance and reliability depend to a large extent on the means employed to drive them. The use of transistors for this purpose should result in efficient and reliable circuits. In the circuits described the Dekatron is driven by a transistor blocking oscillator which, when triggered, produces a pulse of defined amplitude and width, followed by a similar pulse of opposite polarity. A secondary winding on the blocking-oscillator transformer applies these pulses, in the correct phase and amplitude, to the Dekatron guide electrodes. When decades are cascaded, the negative edge of the output cathode waveform, instead of the normal positive edge, is used for triggering the next stage. This system reduces the delay between input and output pulses to a few microseconds, which is the triggering time of the blocking oscillator, and so reduces the error when the Dekatrons are used for counting standard time intervals. For operating a mechanical register two transistors are cross-coupled in a monostable circuit. The register is in the collector circuit of one transistor, which conducts for 0.1 sec when triggered. Since only a small fraction of the supply voltage appears across the transistor when it is conducting, registers requiring several watts can be operated by low-power transistors. The transistor circuits produce accurate waveforms for operating the Dekatrons and registers, enabling the minimum resolving times to be realized.