1438 THE BELL SYSTEM TECHNICAL JOURNAL, NOVEMBER 1953 



pulse occurs in a duplicate set of coincidence tubes. These alternate 

 pulses control the state of the memory circuit. 



The C cycle coincidence circuits are similar except only four triodes 

 are used for the start, and four for the stop pulses. 



Memory and Relay Control Circuits. The memory and control circuits 

 are shown in Fig. 16. The function of the bi-stable memory circuits is to 

 accept the alternate start and stop pulses from the coincidence circuits, 

 switch to the state representing the imposed condition, and hold it until 

 the next successive imposed condition. 



The function of the relay control circuits is to operate or release the 

 relays under control of the memory circuits. The relay control circuits 

 are direct coupled to the memory circuits and one or the other plate is 

 cut-off by the grid bias condition imposed. The relays are in the plate 

 circuits of the control tubes and either have full or no current applied. 

 The operate and release times of the relays add a delay in the contact 



ROO- 



R400- 

 R300-' 

 R200-" 



R100-- 

 R000-- 



-O 

 20 



O 40 

 30 



HUNDREDS 

 SELECTOR 



R30' 



R50 



R400' 



L500' 



L500' 

 R500 



B RELAYS 



START 



COINCIDENCE 



CIRCUITS 



STOP 



COINCIDENCE 



CIRCUITS 



C RELAYS 



START 



COINCIDENCE 



CIRCUITS 



STOP 



COINCIDENCE 



CIRCUITS 



A RELAYS 



• START 

 ■STOP 



Fig. 14 — Time selector schematic. 



