Patent GB-190613312-A (GB)
Title: Improvements in Telephone Exchange Apparatus
Inventor: AITKEN WILLIAM
Filed: 1906-06-09
Granted: 1907-02-14
Abstract: 13,312. Aitken, W. June 9. Indicators or annunciators.-In order to simplify telephone switch-board apparatus, a drum or disk indicator is used,.which is enclosed to prevent the access of dust. Fig. 1 shows a battery indicator, the coil i of which is wound to any suitable resistance and has an iron core with flat magnetic return. The pole-piece 7 partly encircles the drum 4, which is freely suspended and has an iron inset 5 and a suitable counterbalance 6 so that the contact-pin 9 normally takes up the position shown. When the coil i is energized, the polepiece 7 attracts the iron inset 5, which is tapered at the point nearest the pole-piece, so that the drum revolves until it is in magnetic equilibrium, when the pin 9 contacts with the spring 8, thereby completing the circuit of a bell or lamp. When the coil is de-energized, the drum returns to its initial position by gravity. In a modification, the drum is revolved to normal by the insertion of a plug in the spring-jack, which causes a spring to engage a pin on the drum. In further modifications, the drum is rotated by the attraction of a plunger or pivoted armature having a connecting- arm which engages a tooth on the drum. These. indicators are for "calling" and "clearing," being capable of giving three indications, and the coil may be " double wound." The operation is as follows :-When the cores are energized, the armature is attracted and the drum revolves a definite distance by gravity, displaying a calling signal. When the plug is inserted, the drum is restored to normal as described above. When the coils are de-energized, the arm pushes the tooth, forcing the drum to revolve clockwise and displaying the clearing signal, and, on withdrawal of the plug, the spring engages with the lower end of the drum and restores it to the normal. Fig. 11 shows a supervisory indicator combined with a speaking and ringing key. The coils i, i<1> have shaped polepieces 7 and armatures 5 with extensions which engage teeth 'on the drum. A device to hold the signal normally back consists of a lug 15 with a curved channel cut on the inside, and a platform 16 on which a steel ball rests when the drum is free to revolve. The restoring arm 33 is loosely pivoted on a pin 18 and screw 19, but is slotted to slide over both so that it has a left hand and rising motion when the lever 25 is thrown over, and, as this movement is made, the tip of the restoring arm engages a segment of the drum and revolves it to normal, simultaneously throwing the ball into the channel and thus locking the drum. When the coil i is energized, the armature 5 is attracted ; the extension of this armature then engages a tooth on the drum and revolves the drum clockwise, at the same time running the ball by friction out of the channel on to the platform 16. When current is removed from the coil i, the armature 5 falls back until the extension is clear of the tooth and the drum 4 revolves counter-clockwise, showing the clearing signal. Should current be again applied to the coil at this stage, the extension of the armature 5 engages a second tooth and again revolves the drum clockwise. When the current is cut off, the drum again revolves, showing the clearing signal. The lever 25 is.'then thrown over and the restoring arm revolves the drum to normal and by the pin 20 throws the steel ball from the platform into the channel, thus preventing the drum from revolving by gravity. Similar indicators combined with keys are used in junction working, but the rear indicator has extra contacts which are actuated by the armature.