MAGNETIC DRUM TRANSLATOR FOR TOLL SWITCHING OFFICES 741 



former designed for the audio frequency range, and a cold-cathode gas 

 tube. The starter-anode of the gas tube has a dc bias of about +24 volts 

 with respect to its cathode to reduce the value of pulse voltage required 

 to ionize it. When +130 volt battery is applied via the winding of the 

 channel rela.y to the main anode of the gas tube, ionization established 

 in the starter gap by the pulse stretcher signal will transfer to the main 

 gap and cause the relay to operate. Closure of one of the relay make- 

 contacts serves to divert the winding current from the gas tube directly 

 to ground, thereby extinguishing the tube and prolonging its life. Other 

 contacts, not shown, make the registered information available. 



Co7npo7ients 



A full complement of the electronic apparatus described in the last 

 few sections utilizes plug-in components in the following quantities: 



Twin-triode electron tubes 186 



Cold-cathode gas tubes 121 



Germanium varistors 552 



Point-contact transistors 120 



Only one type of each of these components is used in the translator; 

 this uniformity greatly simplifies the maintenance problem and imposed 

 little if any handicap on the circuit designs. 



ADMINISTRATION EQUIPMENT 



Whenever it is desired to add, or to change, a translation item on the 

 drum, the auxiliary administration unit pictured in Fig. 14 is connected 

 to the translator by three shielded cables, shown leaving the rack just 

 under the shelf, and a ten-conductor cable, shown with its plug resting 

 ' on the shelf. The shielded cables convey the a and b sync pulses and the 

 1 once-per-drum-revolution fiducial f pulse to the administrator. The ten- 

 conductor cable, with plug, is used to establish paths extending directly 

 i to magnetic heads on the drum. During the recording of any one com- 

 ! plete translation item on the drum, this plug is successively shifted to 

 each of nine multi-connector jacks located in the amplifier compartment 

 I )f the translator. 



'■ The manual controls are located just above the shelf. At the right are 

 the two keys for ordering a writing operation, one for the a slot and an- 

 other for the B slot of the chosen pair. If either key is lifted, it will order 

 Ihe entry of a magnetic mark (write " 1"). If depressed, the key will order 

 ! the removal of a mark (write "0"). It is obvious that the translation is 



