Patent GB-646439-A (GB)
Title: Improvements relating to automatic telephone systems
IPC: H04M1/274
Filed: 1947-08-14
Abstract: 646,439. Automatic exchange systems. SIEMENS BROS. & CO., Ltd.> and HUMPHRIES, H. E. Aug. 14, 1947, No. 22596. [Class 40 (iv)] An automatic impulse sender for use with a standard dial telephone set has a number of transmitting keys which control the sending of complete impulse trains, each key being allotted to a frequently wanted subscriber. The sender also includes a " pick-up " key for simulating the normal removal of the telephone receiver from its rest and a " cancel " key for restoring the sender to normal before it completes its operation. A loudspeaker reproduces the dialling tone to indicate that a transmitting key may be depressed and also reproduces a locally-generated sig. nal at the completion of impulsing to indicate that the telephone receiver should be lifted, the sender being automatically re-set to normal if either of these operations is not carried out before a predetermined time interval has elapsed. According to the Provisional Specification, the impulse sender may also be used by a manual operator at a P.A.X. or P.A.B.X. As shown in Figs. 1 and 1A, the impulse sender is connected to the exchange line and to the subscriber's telephone set by terminals LA, LB and terminals TA, TB respectively. Each transmitting key SK has an associated marking relay Z and terminals MA-MG which are cross-connected in alphabetical sequence with the appropriate terminals 1-10 to form the desired seven-digit number. For calls requiring fewer digits, the first unconnected marking terminal is connected to the terminal DC. Pick-up key. Momentary depression of the pick-up key PU normally operates relay T and a high-speed voltage testing relay Y which lock. If the voltage is low Y does not operate and a resetting relay CO operates to return the circuit to normal. The resetting relay may also be operated by a cancel key CK or may be operated automatically as a result of tests at a later stage. Relay T closes the subscriber's loop through the input transformer TR of a loud. speaker SPK for reproduction of the dialling tone and over contact t1 operates relays X and K followed by J. General arrangement. A combination of relays P, PA generates impulses when energized either over k2, j4 both operated or over k2, j4 released and l1 operated. The impulses are counted in groups of ten or less by relays A, B, C, D which operate in the order A; B; C; D; D, A; D, B; D, C; D, C, A; D, C, B ; D, C, B, A; relay X preventing double registration of a single impulse. A group of impulses counted with K released is passed to line if relay S is operated and may be termed a digit group. A group counted when K is operated and impulsing contact pa3 is short-circuited at k5 may be termed a pause group. A digit group is terminated by operation of K by a digit marking on one of the terminals 1-10. A pause group is terminated when at the beginning of the eighth impulse contacts a7, c7 open to release K. The end of a pause group and the beginning of a digit group is marked by the release of K and these markings are counted over contact k4 by digit counting relays E, F, G, H and U, which operate in the order E; F; G; U, E; U, F; U, G; U, H; and apply markings in alphabetical sequence to the digit marking terminals MA-MG which are crossconnected to the numerical terminals 1-10. Relay L operates with E when the first digit group commences. The voltage is checked during each digit group by relay Y which is energized over l4 with each operation of P. Predetermined time interval for operation of send key. Following operation of the pick-up key, pause and digit groups are generated alternately to measure a time interval. No impulses are passed to line as S is not yet operated. As digit marking relay Z is not operated, each digit group is terminated at the tenth impulse by K operating over contact s2. The time interval is terminated when relays S and Z are operated over the send-key SK, the impulse counting relays and the digit counting relays being returned to normal by contact s3. Impulse counting starts again when relay T releases and t1 falls back to re-operate K. The resetting relay CO is operated over contact h3 if a send-key is not operated by the end of the seventh pause period. Generation of selected impulse train. Pause groups and digit groups are generated and counted as before except that the digit groups are limited to the impulses generated before K operates over a cross-connection, the impulses being passed to line when S is operated and K released. If a digit group is not terminated by a digit marking, the resetting relay CO is operated over winding (II). Relay CO is disabled by a marking on terminal 10. A transfer relay R locks at the end of a further pause period following the seventh digit and releases all the operated relays, slow-release relay S being the last to fall back. For numbers with less than seven digits, the transfer relay R is operated over terminal DC. Locally generated signal. The voltagechecking relay Y buzzes by self-interruption during the release period of S, producing a short tone signal in the loudspeaker to indicate the telephone receiver should be lifted. This tone signal is also reproduced whenever relay CO is operated except when Y fails to pull up due to low voltage. Predetermined time interval measured after the completion of impulsing. The impulsing circuit is started again at s3 when S falls back and an interval of seven pause groups is measured as before. Removal of the telephone receiver before the time interval has elapsed completes an operating circuit to the winding (II) of relay CO which resets the sender. The exchange apparatus is held by the telephone loop circuit. Transmitting keys. In an alternative arrangement, Fig. 2, adjacent keys such as SKP, SKQ may each have an additional make contact, the additional contacts being series-connected in pairs with a third winding of the resetting relay CO so that the relay is operated by the simultaneous depression of adjacent keys.