1054 THE BELL SYSTEM TECHNICAL JOURNAL, SEPTEMBER, 1953 



and the cold cathode tubes one for each of the channel circuits as pre- 

 viously discussed, and, in addition, the miscellaneous relays through 

 which the operation of the translator is controlled. As already stated, 

 the connection between a translator and the associated decoder is 

 through suitable connector relays which are either a part of the decoder 

 or on a separate connector frame. 



The phototransistors may be adversely affected by temperatures 

 greater than 130°F. Therefore, to provide satisfactory operation during 

 sustained heavy traffic load periods and with high ambient room tem- 

 peratures, an air circulating and filtering unit, as shown in Fig. 13, may 

 be provided. This unit mounts on the translator in place of the regular 

 end cover and otherwise requires no further apparatus change. For 

 convenience in ordering, the "IB" translator is specified when the air 

 cooling unit is desired. Otherwise the "lA" translator will be furnished. 



The translator table contains relays for controlling the dropping, 

 checking, and restoring of the cards in the translator. First are the relays 

 that operate the card "pull-up" and "pull-down" magnets. Then there 

 are select code bar control relays, one for each bar, operated from the 

 sender or decoder, which in turn operate the associated select code bar 

 solenoids. These relays are necessary since the lead resistance from the 

 sender to the translator would adversely affect the operating time of the 

 code bar solenoids. Finally, there are relays that check the code bars for 

 proper operation on a "two-out-of-five" basis. Two, and only two code 



PLUG -IN BASE 



TRANSFORMER, VARISTOR AND 



RECTIFIER PLUS TWO CAPACITORS 



MOUNTED IN THIS PORTION 



Fig. 11 Transistor amplifier. 



