TRAFFIC CONTROL TELEPHONE SYSTEMS Circuit - Sam Hallas
TRAFFIC CONTROL TELEPHONE SYSTEMS Circuit - Sam Hallas
TRAFFIC CONTROL TELEPHONE SYSTEMS Circuit - Sam Hallas
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PART 2<br />
4001-A SELECTOR KEY<br />
Selector Key Case (capacity 40 Keys) comprising 4002-A<br />
Base Unit and 4002-B Extension Unit<br />
Fig. 6.<br />
The function of the selector key (Fig. 8) is to control the operation of the<br />
battery relay and the battery reversing relay of the system, so that the appropriate<br />
sequence of current reversals required to operatethe selector at the station called, will<br />
be transmitted to line. The selector key is operated by twisting the handle P one<br />
quarter turn and releasing it. On release, the key returns to normal driven by a<br />
clockwork mechanism, the speed of which is controlled by a governor Q. At the end<br />
of the shaft and rotating with it, is mounted the impulse wheel A with its coding<br />
segments C. The keys are mounted in a wooden key case, supplied in units with a<br />
capacity for 20 keys. The units may be bolted together if more than twenty keys are<br />
required, as shown in Fig. 6.<br />
The code of the base unit is 4002-A, and the extension unit 4002-B Selector<br />
Key Case.<br />
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