GB865867A - Improvements relating to reversible coupling circuits for counting devices - Google Patents

Abstract

865,867. Electronic counters. ELECTRIC & MUSICAL INDUSTRIES Ltd. May 20, 1957 [May 18, 1956], No. 15491/56. Class 106 (1). A coupling circuit between the orders of a reversible counter comprises two input terminals for receiving carry signals from the lower order, and two valves arranged to assume substantially equal intermediate levels of conduction in the absence of carry signals. On receipt of a carry signal at one terminal the conduction in one valve increases and in the other decreases, and when the signal is transferred to the other terminal a relatively large change of conduction between one valve and the other activates means for developing an output carry signal. As described, input terminals P and Q are connected to the " 9 " and " 0 " cathodes of a multicathode tube stage. A positive signal appearing at terminal P switches conduction in the long tail pair V1 to anode A and raises the voltage of its cathode. This condition tends to be maintained by the rectifier 8 and capacitor 10, so that when the positive pulse is transferred to terminal Q, conduction in V1 is switched over to anode B and this causes a sharp positive pulse at anode A which, applied to a normally biased-off left-hand triode of V2, causes momentary conduction in the latter. The network between anodes C and D of V2 develops two pulses in succession at terminals R and S respectively, and these are used to step on the next higher order multicathode tube. In a subtractive operation a transfer pulse at terminal Q precedes that at terminal P and the latter causes the right-hand side of V2 to conduct, resulting in successive pulses at S and R respectively which effect a " borrow " from the higher order. Specification 812,950 is referred to.