Patent GB-908870-A (GB)
Title: A number sending device for calling frequently wanted subscribers to a telephone system
IPC: H04M1/276
Filed: 1961-04-13
Abstract: 908,870. Keysenders; magnetic core storage matrices. TELEFONAKTIEBOLAGET L.M. ERICSSON. April 13, 1961 [April 13, 1960], No. 13413/61. Classes 40 (4) and 40 (9). The digits of a frequently wanted subscriber's telephone number are keyed into the rows of a storage matrix from which they may be repeatedly read to transmit the number by the actuation of a single push-button whenever required. Thirty such telephone numbers may be stored on as many matrices provided in a single device. The numbers are transmitted as six successive two-out-of-eight tones. Only two of the thirty matrices are illustrated and each comprises six rows and eight columns, two cores in each row marking the, code of a particular digit. Each matrix has a common winding L2 connectible over a rotary switch 122 to a pulse generator 12 which when connected to a matrix by key 121 sets all the cores to saturation. The sense of saturation will be seen to be irrelevant. The row windings of each matrix are selectively connectible by means of number sending keys, such as K and M, to a common interrogation pulse source 11 which is distributed to the matrix row-by-row under the control of a stepping circuit H, 1 to 6, S, and gates V1 to V6. The stepping circuit is governed by circuit 10, which, when a key such as K is operated, transfers the stepping circuit from a suspense state S to a home position H. From the state H the states 1 to S are taken in sequence either by means of regularly occurring pulses PG or, with contacts MS1 broken, by means of pulses from a manual key MS. The manual key MS is used for reading in the digit codes row-by-row. All the matrices have column wires in common associated with the code-writing keys J1 to J8. For any given matrix the cores are first cleared by saturation over the common winding L2 and by controlling the stepping circuit with manual key MS the first row of the matrix may be repeatedly energized by the interrogation pulses from source 11. Each interrogation pulse comprises two portions of opposite polarity and each of a voltage less than the coercive force of a matrix core. In coincidence with a damped alternating voltage, of amplitude less than a core's 5 coercive force, from a source 13 connected to column wires by two code-writing keys J1 to J8, the interrogation pulses cause the demagnetization of a selected two of the cores in the row to a point nearer the centre of the major hysteresis loop. A further actuation of key MS connects the second row of the matrix which is made to register the second coded digit, and so on. The particular row connected up is indicated by the six-lamp display LT. To send the registered number automatically, the key MS1 is set to connect the stepping pulses PG and, when the numbersending key of the wanted subscriber is pressed, the control circuit 10 lifts the stepping circuit out of the suspense state S to home position H from which it steps automatically back to position S where it rests. In each of the states 1 to 6 a matrix row is interrogated, the source 11 cycling demagnetized cores of a row about a fatter minor hysteresis" loop than it cycles magnetized cores. Demagnetized cores, therefore, induce a significant output into the sensing column wires L8 common to all matrices and, with amplifiers F1 to F8, gate an appropriate coded pair of frequencies G1 to G8 to the signalling channel L. The code-writing equipment shown above the dotted line at the top of the drawing may serve more than one number sending device.