GB191211261A - A Graded Service Automatic Telephone System. - Google Patents

Abstract

11,261. Baron, H., [Heimann, G.]. May 11. Automatic exchange systems and apparatus. - A graded automatic-exchange service is obtained by providing various classes of subscribers with impulse - transmitters having various limitations as to the combinations of impulses which they can transmit. Thus a subscriber entitled to connexions only with other subscribers in the same local exchange, numbered 7,000 to 7,999, would be provided with an impulse-transmitter incapable of sending either more or less than seven impulses for the first digit called. Or again, if trunk-connexions to a distant town are obtainable by calling a particular two-digit number, the impulse-transmitters of subscribers not entitled to trunk-service would be made incapable of sending that combination. At a single sub-station, impulse-transmitters giving different grades of service may be provided, and a separate meter for each grade. Prepayment stations may have impulse-transmitters of different grades controlled by coins of different values. Fig. 3 shows a transmitter of fingergrip type in which the transmission of more than seven impulses for the first digit is prevented by the engagement of a stop 103 on the dial 107 with a stop 131 on a bar 100 mounted slidably on the casing 112. The engagement of a cam 109 with pins 120, 121, &c. shifts the bar 100 a step to the left at each rotation of the dial 107, so that the stops 103, 131 do not engage except at the first rotation of the dial. The hanging-up of the telephone withdraws a detent 128 and allows the bar 100 to be returned by a spring 119. In the arrangement shown in Fig. 7, the transmission of less than seven impulses for the first digit is prevented by a pair of short-circuiting contacts 104, 105, which are only opened after a certain movement of the dial has tripped the lever 137 and caught it under a catch 157. This device may be arranged to come into action only at a second or subsequent digit. An arrangement for preventing the dispatch of three and ten impulses successively, for trunk-calling, is shown in Fig. 5. If the dial is first operated for the number 3, a lever 162 carried by the dial is tripped by a finger 168 on the bar 100 and releases a bell-crank lever 178, also carried by the dial, which hooks on to a pin 172 on a lever 166 carried by the bar 100. Consequently, when the dial returns, the lever 166 is displaced and releases a stop 160, which raises into operative position in the path of a stop 161 and prevents the dial from being turned beyond the ninth position at its next actuation. If the dial at its first actuation has been turned beyond its third position, the cam-edge 181, engaging the pin 172, would have restored the lever 178 under the catch 179, and the stop 160 would not have been released. Means are described for restoring the stop 160 &c. when the telephone is hung up.