THE VODAS 



463 



operation. When the armature of relay TM reaches its left-hand 

 contact, relay Hi operates and delays release of the relay train even if 

 TM is at once restored to normal. Hi is delayed in releasing by the 

 time required to charge condenser Ci. The final release of relays 1 

 and 4 is then controlled by the time constant of an auxiliary circuit 

 involving relay H2 and condenser C2, while that of relays 2 and 5, 

 which is made later so as to suppress delayed echoes, is controlled by 

 the circuit charging C3. On the receiving side, condenser C4 is ad- 

 justable so as to permit the technical operator to select the shortest 

 release time for suppressing the delayed echoes in a given land line 

 extension. 



Fig. 4 — Type A control terminal at San Francisco. 



The vodas control terminal of the A type ^ used at New York con- 

 sists of a line of technical operating positions with cross-connections to 

 other lines of equipment containing the delay units, repeaters, vodas 

 amplifier-detectors and privacy apparatus. Figure 4 shows an 

 arrangement of a single terminal at San Francisco. The control bay 

 is placed between two line testing bays on the left and two trans- 

 mission testing bays on the right of the operating lineup. The dis- 

 tributing frame is in the center of the picture; and repeaters, ringers 

 and privacy apparatus are shown at its left. At the extreme left is 

 the vodas bay. 



