724 THE BELL SYSTEM TECHNICAL JOURNAL, MAY 1956 



these input terminal there is a complementary terminal to which are 

 applied negative-going pulses from one of the drum memory reading am- 

 plifiers. As will be explained later, advantage is taken of this comple- 

 mentary arrangement to obtain a signal indicating a match between 

 either, (1) an operated code relay and a pulse from the reading amplifier, 

 or (2) a nonoperated relay and no pulse from the reading amplifier. All 

 of these signals, from 40 sections of the match units, are combined in a 

 cascade of "and" gates; when all indicate a match, the translation se- 

 lecting unit delivers an output "match" pulse. 



Since this match pulse is not strong enough to enable 40 gates in the 

 output channels, it is passed to a "pulse generator" (a regenerative pulse 

 repeater) which produces, virtually coincident in time, a powerful "a" 

 gate-opening pulse. Note that both the "a" and the similar "b" pulse 

 generators are enabled to operate only when the input code is authentic, 

 as evidenced by the operated code check relay cbkm. 



In an unrestricted magnetic drum translator design this identifying 

 pulse would cause immediate registry of part of the desired information. 

 Here, however, is evidenced one of the penalties for having a direct one- 

 for-one substitution for a card translator. The decoder and card transla- 

 tor function in a definite sequence; one of the steps in this sequence is 

 initiated by the ind signal from the translator which informs the decoder 

 that the selected card is properly "indexed" so that it may be "read." 

 Therefore, in the case of the drum translator, to preserve this sequence, 

 the selected translation is permitted to pass unheeded, except that the 

 IND signal is synthesized from the identifying b gate-opening pulse. This 

 operation closes one relay, indb, through a special output channel (top- 

 most one in Fig. 4) provided for the purpose. The decoder, thus notified 

 that the desired translation is available, applies battery to its register 

 relays, and the output channels are completely enabled for a subsequent 

 registry of the desired information. 



The output information is usually registered during its next passage, 

 one drum-revolution after initial identification of the item. The action of 

 identifying the translation is again as described above, and there remains 

 only to follow the operation in the output channels. E\'en before the 

 translation selecting unit has initiated the identifying gate-opening 

 pulse, reading amplifiers which are required to deliver an output code 

 have each commenced delivery of a pulse to their corresponding gate 

 terminals in the and gate and pulse stretcher units. (See Fig. 4). When 

 these pulse signals have reached a stable maximum, the gate-opening 

 pulse (a or b depending on the slot which is being read at the moment) is 

 free to pass through the gates and to trigger the pulse stretchers. The , 



