Patent GB-1173600-A (GB)
Title: Switching Control System.
Inventor: WESTERHOFF DAVID HERMAN
IPC: G09B5/12
Filed: 1966-11-12
Abstract: 1,173,600. Audio teaching system. OMNILAB Inc. 12 Nov., 1966 [12 Nov., 1965], No. 29649/69. Divided out of 1,173,599. Heading H4R. In an audio teaching system each student position has a number sender, e.g. digit pushbuttons or a telephone type dial, by the operation of which a central switching network may be controlled to connect a reproducer at the student position with the selected one of a number of stored programmes in a central programme library. Each student position is connected to a corresponding switching assembly of selectors, and any number of student positions may be connected by their respective switching assemblies to the same stored programme. Figs. 2 and 3 show the digit pushbuttons 18 at a students position 10 and the respective switching assembly 22 which are interconnected by the wires 0-9, N, 11 and 12. The switching assembly 22 includes a rotary selector S1 having switch banks A1 to M1 of which the contacts of banks C1 to M1 are connected to respective programmes in the programme store, e.g. of which, in the described embodiment, there are 200. In operation the student selects the particular programme he wishes to hear by depressing the appropriate digit buttons in sequence. Each depression of the button removes an earth from the respective line 0-9 and puts an earth on line N, while the button is held depressed. The first button to be depressed will either be a " 0," for a programme 0 to 99, or a " 1," for a programme 100 to 199. On depression of button O the earth on line N cocks stepping cam switch relay CS, ready to step when the earth is taken from line N and also causes S1 to start stepping, since a circuit for the coil S1 is completed via the line 68 and the wiper of bank B1. As soon as S1 steps on to the first position however, the circuit is broken via line 68 and the wiper contacts line 69 instead, which is however, connected at terminal block 54 to the pushbutton line O, which is open circuit to earth, and so S1 stops stepping. If the button 1 had been pressed, line 69 would have been earthed and S1 would have stepped on over all the commoned contacts of B1, and over the contacts connected to line 70, which is jumpered on block 54 to push-button line O, until the wiper rested on the first unconnected contact on bank B1. When the first button is released, each is removed from line N and stepping cam switch CS is stepped on to its first position, in which position it reverts a tone T1 over contacts 75 of the cam switch to the student's audio reproducer at terminals 16 to indicate completion of the first switching operation, it inhibits operation of selector switch S1, and puts selector switch S2 in a position to operate on the next operation of a digit push-button. Thus on the selection of the next digit the earth placed on line N by the push-button operation, cocks the cam switch relay CS, and causes selector S2 to step until the wiper of bank A2 reaches the contact connected to that line from which earth has been removed by the depression of a digit push-button, the corresponding stepping of bank C2 connecting line 40 with that bank of banks C1 to M1 corresponding to the 10's digit selected. Release of the push-button completes the stepping of cam switch CS, reverts tone T2 to the student's audio reproducer, inhibits selector S2, and readies S1 so that the next operation of a digit push-button will cause the stepping of S1 from either its first contact position, if a " 0 " was the first digit selected, or its middle contact position if a " 1 " was the first digit selected, to the first contact connected to a line from which earth has been removed by the operation of a digit push-button, this completing the connection of line 44 to that one of the contacts on the banks Cl to M1 of selector S1 which is connected to the programme selected by operation of the push-buttons. Release of the last push-button steps cam switch CS so that the programme on line 44 is connected to the student's audio reproducer at terminals 16. The final position of the cam switch CS may also cause the programme to be reproduced and allow some or all of the student's pushbuttons to be used to control other apparatus, e.g. a tape recorder. After the programme has ended operation of the clear button CL causes energization of the selectors S1 and S2 and the cam switch CS via their " off-normal " contacts so that they revert to their initial position. The push-buttons 57 may be replaced by a telephone type dial 20, in which case the full line interconnections on terminal block 54 are replaced by those shown dotted. The operation of the dial is similar to that with the pushbuttons with the " off-normal " contacts 110 stepping the cam switch CS once for every operation of the dial, and the digit contacts 111 stepping switches S1 and S2 at the appropriate times. If it is desired to increase the programme storage capacity an additional switching module may be added to each student's switching assembly. The additional module comprises, as shown in Fig. 6, selector switches S3, S4 and S5, and is connected to the terminal block 54 of the normal switching assembly of Figs. 2 and 3. In operation, the first button to be pressed causes S3 to step, energized initially over line N, until the wiper of bank B3 contacts the line which is O/C due to operation of the corresponding push-button. By operation of S3 the banks A3 and C3 are now operative to select the appropriate one of selectors S1, S4 or S5 in accordance with the 100's digit selected. During movement of S3, delayed relay R1 is operated to prevent any wrong operation of selectors S1, S4 or S5, while the contacts of S3 are sweeping over the activating contacts of those selectors. When S3 wipers reach the correct position relay R1 is no longer pulsed and, with its contacts closed, the ground path to the appropriate selector is made. Operation of the second button causes the selection of the appropriate bank of contacts in selectors S1, S4 and S5, as previously described while on operation of the third button the selector selected by S3 is stepped to the appropriate programme terminal, and on release of the button the programme is connected to the student's audio reproducer.