Patent GB-190713175-A (GB)
Title: Improvements in Electric Selecting Apparatus for Telephones and the like.
Inventor: WATKINS WILLIAM DAVID
Filed: 1907-06-06
Granted: 1908-01-23
Abstract: 13,175. Watkins, W. D., Bolster, J. W., and Goodsell, W. E. June 6. Telephone systems; telegraphs.-By means of the described selective apparatus for use mainly on telephone lines, but applicable also on signalling circuits generally, any telephone in a party-line system may be connected with the main line, while the circuits of all the remaining subscribers on the party line are broken. Each telephone on the line is equipped with one of the selecting - devices, and these are placed under the control of the operator at the central station, who, by sending through the line a series of electric impulses corresponding in number to the number of the substation with which connexion is desired, may connect that station to the main line with the exclusion of all other stations along the line, with the exception of the calling station. The current impulses sent along the line energize all the electro-magnets 11 of all the instruments on the line, excepting the magnet of the instrument at the calling station, the circuit for which has been broken by tho removal of the receiver from its hook. The energization of the magnets 11 causes the polarized armatures 12 to rotate slightly on their pivots 13, and thereby causes the selecting-arms 16 to move upwards. In the normal position of the arm, a pin 24 on the arm 16 rests against the first plate 25 of a series of shaped plates mounted on the block 18. When the arm receives its first upward movement, it is also moved to the right due to the engagement of the pin with the shaped plate 25, and the contacts 30, 29 move apart and thus break the calling circuits of all the telephones except that of the calling station, the magnet of which has not been energized. Each movement of the armature by the magnet lifts the pin 24 above the upper edge of the lower plate 21, and when the armature drop the arm, due to the arrangement of the plates 20, 21, takes up a new position, with the pin 24 resting between the first and second lower plates 21. Each energization of the magnet from the central station moves the selecting-arm one stage forward. Each apparatus has a series of contacts 32 ... 35, Figs. 1 and 6, for the calling and talking circuits, which are set in different positions on each instrument, the position corresponding to the number of the instrument. When the proper number of impulses has been sent, the magnets are finally de-energized, and a pin 38 on the selector arm of the called station engages with the contacts 32 ... 35, and thereby closes the calling and speaking circuits. At the close of the conversation, the central station is notified, whereupon the operator sends a current through all the magnets 11, in the opposite direction to that of the momentary selecting currents; the magnets are thus re-energized and the polarized armatures 12 move in such a way as to draw down the selecting arms 16, till the pins 24 are below the lower edges of the plates 21, whereupon, under the influence of the springs 28, the arms assume their initial positions, and the line is clear for any subscriber to call.