Patent GB-383166-A (GB)
Title: Improvements in and relating to dial switches
IPC: H04M1/677
Filed: 1932-04-06
Abstract: 383,166. Impulse transmitters. FULD & CO. TELEPHONUND TELEGRAPHENWERKE AKT.-GES., H., 136, Mainzerlandstrasse, Frankfort-on-Main, Germany. April 6, 1932, No. 9884. Convention date, April 13, 1931. [Class 40 (iv).] The shaft of a dial transmitter carries a number of spring - controlled rotary cams operated by the dial and adapted, when certain predetermined digits are dialled, to prevent mechanically the emission of impulses. With the construction shown, emission of impulses when the second of the digits 09 is dialled is prevented and the transmitter is also locked against further operation until the receiver is replaced. The dial shaft W loosely carries three cam discs L1, L2, L3, shown separately in Figs. 3 to 5, held in normal position by spring action against a projection A of a spring- controlled lever Sp. For all digits, except those interdicted, the projection A is held up by the disc L1 so that a projection P thereon is prevented from dropping between and spreading the impulse springs J. When an interdicted digit is dialled, projection A drops into a deep recess between projections B1, C1 on disc L1 so that lever Sp falls and spreads the impulse springs. At the same time, the lever rotates a dog Q into engagement with the driving gear and locks the dial. The lever and dog are released when the receiver is replaced on the switch hook H. In a modification interdicting a single initial digit, the disc L2 is omitted. Operation for permissible digits 1 .. 9. When the dial is operated, a spring-controlled pawl K on shaft W engages notches 01, 03 (normally in register) of discs L1, L3 and moves these discs into a position dependent on the digit dialled but in any case not through a sufficient angle for pawl K to engage abutment p2 on disc L2. The limiting position when digit 9 is dialled is shown in Fig. 7 (left), disc L2 being in normal position. On the return movement, discs L1, L3 return under spring action but L1 remains slightly off-normal as shown in Fig. 7 (right). The operating notches 01, 02, 03 in the discs are now out of register so that on further dialling the pawl K rides over one or other of the discs without engaging the notches, the discs remaining stationary. For digits 1 .. 9, disc L1 is not rotated through a sufficient angle to enable the projection A of lever Sp to drop into the deep recess in L1. Permissible digits 01 .. 08. When the transmitter is set by dialling 0, the discs assume the position shown in Fig. 8 (left) in which L2 is moved (in addition to L1, L3) so that on the return movement L3 goes to normal, L2 remains slightly off normal, while L1 is held by shoulder D1 substantially in its operated position, Fig. 8 (right). When the next digit is dialled, L2, L3 move (since notches 02, 03 are in register) to the position shown in Fig. 9 (left), but as the digit does not exceed 8, L1 remains in the position to which it was last set. On the return movement L2 remains a further step off-normal, notches 01, 02, 03 are out of register, Fig. 9 (right), and further dialling is without effect on the discs. Interdicted digits 09. After the first digit has been sent out, the discs are as shown in Fig. 8 (right) as described in the preceding paragraph. On dialling 9, L1 is moved (through abutment p1) as well as L2 and L3. The projection A on lever Sp is now more or less opposite the deep recess in L1, Fig. 10 (left), but is for the present held up by a cam E fixed on the dial shaft. On the return movement, Fig. 10 (right), a cam E moves back and A drops to permit Sp to spread the impulse springs to lock the dial. Permissible digits 00. The second digit 0 moves disc L1 past the position shown in Fig. 10 so that it is held by abutment B1 and projection A so that impulsing is not interfered with.