CARD TRANSLATOR FOR NATIONWIDE DIALING 1049 



CARDS 



LIGHT 

 SOURCE 



LIGHT 



Fig. 6 — Block diagram of channel circuit. 



cards in their normal positions they are aligned and the holes in the 

 cards form unobstructed, horizontal tunnels called channels through 

 the entire stack. When a particular card has been selected and dropped 

 a distance slightly greater than the height of an unenlarged hole, these 

 light beams through all of the channels are blocked by the dropped card 

 except for those holes which have been enlarged. This results in a pattern 

 of clear channels which represents the translator output information. 

 The change in the silhouette of the stack from the condition of all 

 cards normal to that of one card dropped is shown in Fig. 5. 



THE CHANNEL CIRCUIT 



Fig. 6 is a block diagram of the circuit used to determine whether a 

 particular channel is interrupted by a dropped card or not. Each block, 

 with the exception of the light source, represents a piece of equipment 

 provided individually for each channel. The light source is common to 

 all channels. If the hole in the dropped card for a particular channel has 

 been enlarged, the light will pass completely through the stack of cards 

 and fall on the phototransistor. The phototransistor converts the light 

 into an electrical signal which, after being increased by the transistor 

 amplifier, is used to trigger a cold cathode gas tube. The gas tube in turn 

 operates the channel relay. This relay is located in the associated equip- 

 ment which uses the information supplied by the translator to process 

 the call. 



In making a detailed examination of the channel circuit, it is con- 

 venient to consider it in two parts: the optical section and the electrical. 

 The optical section includes everything up to the point where the light 

 falls upon the germanium of the phototransistor. This part of the chan- 

 nel is shown functionally as Fig. 7. The light source is a standard pro- 

 jection type lamp normally rated at 500 watts. To obtain long life it is 

 operated in the translator at about half of its rated voltage at which 

 level its input is approximately 170 watts. This type of lamp was 

 chosen because of its high concentration of light in a small plane 

 area. 



The light from the lamp passes through a motor driven perforated disc 

 which modulates it with an approximate square wave at a 400-cycle 

 rate. Modulated light is used because it is more economical to use ac 



