594,642. Pulse counting circuits. NATIONAL CASH REGISTER CO. May 19, 1944, No. 9750. Convention date, March 22, 1943. [Class 40 (v)] A number of trigger-connected pairs of hard valves are arranged in a chain, the chain connections being such that the pairs respond in a predetermined sequence to pulses applied to all the pairs, each pair, after actuation becoming unresponsive until the next pair has been actuated, thereupon restoring to the initial condition. Double triodes 10, 11, 12 cross-connected by resistance condenser' combinations 31, 32, 33, 34 are maintained with one section only conducting. Keys 47, 50, 53 are depressed, temporarily earthing the grids and causing sections A of valves 11 and 12 and B of valve 10 to conduct, the anode of A section of valve 10 assuming a higher potential than that of valve 11. Due to the connection 36, 37 between succeeding valves, the grid of the B section of valve 11 assumes a higher potential than that of valve 12. A negative pulse, applied over conductor 57 to the grids of the A sections of all the valves, causes valve 11 to reverse its state in preference to valve 12. The pulse is ineffective on valve 10 since the A section is conducting, but due to the resistance condenser connection 71 the fall in anode potential of B section of valve 11 causes the grid potential of B section of valve 10 to fall so that valve 10 reverses its state. Connections 80 may be taken from the valves to control an indicator or for determining the state of the ring. Specification 600,503, as open to public inspection, is referred to.