Cyclopedia of Telephony and Telegraphy a General Reference Work on Telephony, Etc. Etc. (Volume 2)

Excerpt: ...corresponding to them are off-normal. Simple tests then suffice to show whether they are properly or improperly in their off-normal position. Release of the First Selector. As will be shown later, the normal way of releasing the switches is from the connector back over the release wire. It is sufficient to say at this point that when the proper time for release comes, an impulse of current will come back over the second selector trunk release wire through the private wiper, to the back release relay magnet, and thence to ground through the third wiper of the side switch which is in its third position. It may be asked why the back release magnet was not energized during the previous operations described, when current passed through it. The reason for this is that in those previous operations the private magnet was always included in series in the circuit and on account of the high resistance of the private magnet, sufficient current did not pass through the back release magnet to energize it. When the back release relay is energized, it closes the circuit of the release magnet and thus, through the link 11, draws the double dog away from its engagement with the shaft ratchets and at the same time, through the link 12, restores the side switch to its normal position. Whenever the release magnet is operated it acts as a relay to close a pair of contacts associated with it and thus to momentarily ground the release wire of the first selector trunk extending back to the line switch. Referring to Fig. 389, it will be seen that this path leads through the contacts 13 and 14 and the release magnet to the battery. It is by this means that the line switch is released, the release impulse being relayed back from the first selector. Second Selector Operation. For the purpose of considering the action of the second selector, we will go back to the point where the first selector had connected with a second selector trunk and where Page 183 its side switch had...