MAGNETIC DRUM TRANSLATOR FOR TOLL SWITCHING OFFICES 725 



latter devices, each containing a single transistor in a monostable circuit 

 arrangement, deliver 12-volt pulses lasting about a millisecond. The 

 pulse stretchers from which an output code is not required are not trig- 

 gered, owing to the absence of pulses from the corresponding reading 

 amplifiers. 



The remainder of the output channel, as previously stated, is borrowed 



directly from the card translator, and the action is similar. In the output 



detector, a transformer steps-up the 12-volt pulse signal to a voltage more 



than sufficient to establish a discharge in the control gap of a cold-cathode 



gas tube. Since the decoder has applied voltage through a relay coil to 



the main gap, the discharge transfers, and the resultant current flow 



operates the relay. The operated relay, which may be in the decoder, 



registers the code and locks to ground through an auxiliary contact. This 



' action also extinguishes the gas tube, thereby extending its life. 



: Except for relay operation, all of the activity described here for two 



drum revolutions repeats itself for every subsequent drum revolution 



I for as long as the code check relay cbkm remains operated. However, 



! once the code is registered, no further use is made of the pulses in the 



output channels. 



When the decoder has made use of the translation, it transmits a sig- 



I lull which is used in the code-check relay system to indicate when all re- 



;lays are properly restored. In the card translator this signal is also used 



to restore the selected card, but in the drum translator this operation, 



of course, is not required. 



. idministration Equipment 



I 



To utilize the magnetic drum translator as described above, it is obvi- 

 ous that some means for writing-in the translations is as necessary to 

 t he drum as a card punch is to the card translator. Although a selective 

 S writing, or "Administration Unit" was required, a highly efficient design 

 \\ as not essential to the experiment. Consequently there was constructed 

 a separate, portable aggregation of essential basic electronic circuits, 

 ; arranged for manual control, but designed with a view to possible ex- 

 'leusion to fully automatic operation. This equipment will be described 

 ill a later section. 



I QIJIPMENT AND CIRCUIT DESIGN DETAILS OF THE TRANSLATOR 



(nticrdl Description 



'i'lie entire translator is mounted on an 11-foot by 32-inch bay and has 

 licen made to conform to telephone central office practices as far as pos- 



