. Electronic apparatus for biological research. Electronic apparatus and appliances; Biology -- Research. COUNTERS This seemingly complicated behaviour can be achieved quite simply v^'ith the help of an extra pair of diodes in a circuit due to Rotblat, Sayle and Thomas^. The relevant fragment of circuitry is shown in Figure When the fourth circuit is 'off', the right-hand triode is conducting, Dg is cut off and pulses are transferred from the fourth to the second Eccles- Jordan circuit via D^. When the fourth circuit is 'on', the right-hand anode rises to HT+, rendering D^ conductive. A
. Electronic apparatus for biological research. Electronic apparatus and appliances; Biology -- Research. COUNTERS This seemingly complicated behaviour can be achieved quite simply v^'ith the help of an extra pair of diodes in a circuit due to Rotblat, Sayle and Thomas^. The relevant fragment of circuitry is shown in Figure When the fourth circuit is 'off', the right-hand triode is conducting, Dg is cut off and pulses are transferred from the fourth to the second Eccles- Jordan circuit via D^. When the fourth circuit is 'on', the right-hand anode rises to HT+, rendering D^ conductive. At the same time, the left-hand anode is now negative to HT+, D^ conducts and cuts off D^. In this manner pulses arising from Eccles-Jordan No. 1 are directed to Eccles-Jordan No. 4 and blocked from Eccles-Jordan No. 2 (for further details the original From first Eccles-Jordan. Fourth Eccles-Jordan circuit Figure article should be consulted). Scale of ten counters can be connected in chains to form scales of 100, or 1,000 and so on. A cheaper kind of scaler, using Eccles-Jordan circuits but relying on capacitors instead of diodes for coupling, has been discussed by Gottlieb^. It seems to the author that circuits of this kind might be rather more difficult to get going than the diode-coupled variety. Eccles-Jordan design procedure has been considered by Taubio. Scalers of the Eccles-Jordan type are reliable and widely used, but they contain a large number of valves, and special decade counting tubes have been developed to effect simplification and gain economy here. These have been reviewed by Kandiah^^. Briefly, they fall into two categories: (1) Glow discharge types in which a glow occupies one of ten positions, circularly arranged, in a soft valve. Each input pulse moves the glow on to the next station, and the count is read off" by observing the position of the glow against an external annular numbered escutcheon. At the com- pletion of each complete circuit of the
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