Patent GB-190304323-A (GB)
Title: Improvements in Selecting Devices for Telephone Systems and other Purposes.
Inventor: WATKINS WILLIAM DAVID
Filed: 1903-02-24
Granted: 1903-06-04
Abstract: 4323. Watkins, W. D. Feb. 24. Telephone calls.-Relates to electric selecting- devices adapted, more particularly, for enabling a subscriber on a telephone party line to ring up any other subscriber with whom communication is required. If the subscriber to be called up is number 5 on the line, the calling-subscriber has only to close the circuit four times in quick succession with a pause at the fifth contact. The supporting- frame 2 of the selecting-device is stamped from sheet brass or other diamagnetic metal, arms 4, 5, 6, 7 being stamped and bent as shown. The cores of two electromagnets 9 (of which one only is shown) are secured to the frame 2 by screws passed through openings 8. The outer ends of the cores are connected by a plate 12 formed with lugs 13 for the pivot serews of the polarized armature 15. The permanent magnet (not shown) is secured at 10 to the plate 2, and its front end is bent down at right-angles opposite the armature 15. The clapper rod 16 of the bell is secured to the armature 15, but the rod is normally locked against movement by a tongue 24 projecting upwards from the pivoted bar 22 through a slot 25. A catch 27, pivoted at 29 and weighted at 28, normally holds the bar 22 in the raised position shown in Fig. 1. Opposite the rear ends of the electromagnets is a soft-iron armature 19, pivoted at 20 and serving to actuate a pawl-bar 60 bearing pawls 64, 65. A "locking disc" 37 and a "guard disc" 38 are journalled in the arms 6. Both discs have light coiled springs on their spindles, which tend to restore them to the positions shown in Fig. 1 after movement. The locking-disc has a notch 42, and is provided with perforations 44 for the adjustment of an arm 46, which is permanently set at a certain distance from the notch 42 depending on the number of the subscriber. When the calling- subscriber closes the circuit, the soft-iron armature 19 is attracted, and the pawls 64, 65 actuate both discs 37, 38. The pin 50 passes to the opposite side of a bell-crank lever, rocking it idly as it passes. The pin 51 releases the pawl 48, and allows its other end to engage with the teeth of the disc 37 under the pressure of a spring 49. The pawl 65 escapes from the teeth of the wheel 38 when at its extreme right-hand position, but, as the contacts are made and broken rapidly by the calling-subscriber, the bar 60 returns before the disc 38 has time to reverse its movement. The disc 38 is therefore merely oscillated by the pawl 65, while the disc 37 rotates step by step. The last contact made by the calling-subscriber is a prolonged one. This gives the disc 38 time to rotate under the influence of its spring, and the pin 50 rocks the bell-crank lever so as to lift the weight 28 and release the bar 22. These movements are common to all the instruments on the party line. In the case of the subscriber who is being called, however, the notch 42 is at this moment immediately beneath the bent end of the bar 22, which drops into it, thus releasing the clapper 16 and allowing the bell to ring. A finger 30 extending from the armature 19 restores the arm 22 to the locked position when the electromagnets are de-energized.