GB185848A - Improvements in electric calling devices - Google Patents

Abstract

185,848. Whistlecroft, A. W. June 13, 1921. Selectors.-A calling-device, adapted to beoperated by a certain sequence of wireless im pulses of predetermined length, is so designed that signals of shorter or longer duration are rendered ineffective, whilst signals of the correct length are stored up, notwithstanding the intervention of jamming signals, and actuate the alarm when the predetermined number have been received. Energy from the receiving-aerial energizes an electromagnet g, Fig. 1, and rocks a pivoted arm h so as to free a friction disc d<1> mounted on a clockwork-driven spindle b. An impulse of considerable duration allows the governor e, f to gain speed and lift a sliding collar d sufficiently to close a contact j<a>, j, thereby energizing a clutch magnet k, and causing a spindle m to be rotated from a wheel l driven by the clockwork. An impulse of the correct length rotates an arm o, carried by the spindle m, sufficiently to close a contact (not shown) which energizes a magnet q, Fig. 3, and thereby moves a pawl t forward over one tooth of a sector u. Each time a, signal of the correct duration is received, this operation is repeated, until finally contact v, v<1> is closed and operates the alarm. Simultaneously, a magnet x is energized to release a locking-detent w, and allow the sector u to be reset by a spring u<1>. Should the received impulse exceed the correct duration, a second stop on the arm o energizes a cocking-magnet s, Fig. 3, which lifts the arm of the pawl t out of contact with the teeth of the sector u, and causes the return stroke to be ineffective in that it does not rotate the sector. Quite short impulses do not release the brake-disc d<1> sufficiently to allow the governor e, f to gather speed enough to close the contact j. The same contact that actuates the cocking- magnet s also energizes a safety magnet y, Fig. 1, which, by closing a contact z<b>, operates a magnet z<c> to bring down a clamping-arm zd and so stop the motor, thereby preventing the motor from running down during signal-impulses of very long duration. The contact z<b> is maintained closed until the armature z is freed from a stepped portion of the bar z<a>. This release is effected by means of an arm h<a>, when the armature-arm h is finally raised on the cessation of the signal. As soon as the motor is stopped, the contact j is broken, the spindle m is declutched from the wheel l, and the arm o flies back to its initial position under the influence of a spring. According to the Provisional Specification, the apparatus may be modified to work with timed intervals as well as timed impulses by the addition of another clock-work train set into motion by the registration of the first correct signal.