Patent GB-191121815-A (GB)
Title: Improvements in or relating to Telephone Systems.
Inventor: DERRIMAN WALTER HOWLEY
IPC: H04M1/272
Filed: 1911-10-03
Granted: 1912-10-03
Abstract: 21,815. Derriman, W. H., [Automatic Electric Co.]. Oct. 3. Automatic and semiautomatic exchange s y s t e m s. - Instead of successively operating a single impulse sender for the different digits of the required line, separate senders for each digit are used and are mechanically interconnected in such a way that after setting manually each is locked until the preceding one has reached its normal position. Each individual sender comprises a rotary dial which, when set by hand, carries a pawl freely over the teeth of a crown wheel, which is geared to a spindle operating the impulse-spring. The invention is described as applied to a two-wire semi-automatic system. Construction of impulse-transmitter. Figs. 4, 6 show top and bottom views of a portion of the transmitter, Fig. 7 being a top view of one of the units with the dial removed. A member 15 provided with a spring tongue 16, Figs. 4, 7, is secured to the under side of the rotary finger dial 3 and co.operates with a wheel 7, which has spur and crown teeth and is loosely mounted on the spindle of the dial, in such a way that during the setting of the dial the tongue 16 slips over the crown teeth, but in its return movement the tongue 16 drives the wheel 7, which is geared to a centrifugal brake 13, 14, Fig. 6, and to a cam 11 controlling the impulse springs 18, 19. In setting the "thousands" finger dial, an arm 21 is pressed by the finger against a stop 22, thereby causing an arm 25, Fig. 6, to lock the brake spindle 12 of the "hundreds" impulse-sender. A lug 34 on an arm 24 rigid with the arm 25 is thus brought under a shoulder 37 on a catch lever 33, so that the " hundreds" sender is locked when the finger is removed from the arm 21 and remains so until the catch 33 is tripped by the return of the "thousands" finger dial to normal. A similar mechanical relation exists between the "hundreds," "tens," and "units" senders. To retard the release of one sender after the preceding one has returned to zero, pivoted pawls 31 on the arms 24 ride over and ergage shoulders 32 on a shaft 28 provided with a dash-pot 29. General operation of system. In response to a call from the subscriber A, the insertion of the answering-plug P<1> causes the cut-off relay 78 to energize in series with the clearing-relay 79. Upon finding the number of the subscriber required, the operator inserts the plug P<2> into the jack of a first selector trunk 83, 84, and throws the key K<1> so as to bridge the impulse-springs 18<a>, 19<a>, 18<b>, 19<b> &c. of the digit senders across the trunk. She then sets the senders in turn, without waiting for their return to zero. The successive operation of the impulse-senders in the manner described causes the operation of selectors and connectors substantially as described in Specification 1298/10. When all the impulses have been sent, the operator releases the key K<1>, thus bringing a polarized relay 45 across the trunk, this relay being energized by current over the selector trunks and the line relay of the connector. The clearing lamp 139 is thus lighted. When the called subscriber replies, a pole changing relay at the connector reverses the battery connexions of the line relay, so that the polarized relay 45 opens the circuit of the lamp 139. Clearing signals are given by the lamps 155, 139 when the subscribers replace their receivers. Specification 1421/10 is referred to.