Patent GB-191204179-A (GB)
Title: Improvements in or relating to Telephone Systems and Apparatus therefor.
Inventor: MELLINGER EDWARD ARTHUR
IPC: H04M1/274
Filed: 1912-02-19
Granted: 1913-02-19
Abstract: 4179. Mellinger, E. A. Feb. 19. Automatic exchange systems and apparatus.- In order that a subscriber may readily call certain other subscribers with whom he frequently desires connexion, the numbers of these subscribers are set up by means of pins, projections, notches, or the like, so that by means of a single operation the necessary sets of impulses are sent for each digit of the wanted subscriber's number. Means are provided for indicating to a calling subscriber, without removing his receiver, when the called subscriber answers, or, if he is busy, for giving a special busy signal. If the called line is busy, the entire connexion is automatically released by momentarily opening the line circuit at the connector, thereby opening the circuit of a selfholding relay at the sub-station which finally opens the line circuit. The answering and busy signals, and the busy release, can be used with impulse-transmitters of the usual type. Impulse-transmitters. Fig. 1 shows one form of the first device, in which the numbers of the subscribers to be called are set up by horizontal rows of pins 15 on a vertical board 1, the top row being shown set up for subscriber No. 5323. A movable bar 3, which is connected to weights 6 by cords passing over pulleys 5 so that it can be set in any position in the racks 2, carries a sliding block 7 connected to a weight 11. The block carries a pair of springs 8, 9, Figs. 3 and 4, of which the spring 8 is cut away at its end so as to form a U-shaped portion through which the spring 9 extends. At the bottom of the board, four pin cylinders 23, 24, 25, 26 are arranged as shown, so that any additional number can be set up. To call a particular subscriber, the bar 3 is moved to the corresponding horizontal row, and the block 7 is moved to the right so as to raise the weight 11, and is then released. As the spring 9 engages the pins 15, the contact between the springs 8, 9 is opened. While the block 7 is moved to the right, the springs 8, 9 are short-circuited by an auxiliary switch 16, which is moved to open this circuit when the sliding rod 20 engages the side walls 2. In modifications of the impulse-sending device, the bar 7 may be fixed and the board 1 movable, or the pins may be arranged radially on a rotatable disk. In another form, a disk is provided for each subscriber, and pins project from its periphery to represent the subscriber's number. The contact-device slides on a notched bar so that it can be brought opposite any desired disk, and comprises a pair of springs 46, Fig. 12, normally in contact but mechanically connected to a pair of springs 47, which are separated by the pins projecting from the periphery of the disks so as to open the contact 46. In another form, the subscribers' numbers are represented by notches in a metal plate which is passed through an impulse-sending device. The calls may be repeated at suitable intervals by clockwork mechanism. Instead of connecting the contact springs to the two sides of the line so that the impulses are sent by separating the springs, the apparatus may be connected as a shunt to the ordinary impulse-sender which is operated in such a way that it would normally send the maximum number of ten impulses time after time for each digit; this is prevented by the arrangement of code projections which shortcircuit the springs of the impulse-sender as soon as the required number of impulses have been sent. System. In order to indicate to the calling subscriber, while his receiver is still on its hook. when the called subscriber answers, or if he is busy, and in the latter case to release the connexion, the sub-station circuits include a neutral relay 81 and a polarized magnet 82 controlling a set of springs 87, 88, 89, and the shaft of the calling apparatus carries two arms 91, 92 controlling the springs 84, 85, 86. The exchange apparatus is assumed to be the same as is described in Specification 1298/10, except that the relay 272, energized when the called line is found to be engaged, is provided with extra contacts 95, 96, which energize a relay 97, thus opening the trunk connexion at springs 99, 100 for a sufficient time to give a signal to the calling subscriber and bring about the release of the connexion. When one subscriber calls another by the additional calling-apparatus, the first movement of its shaft causes the arm 91 to close contacts 84, 85, thus completing a circuit from line 157 through contacts 101, 46, 84, 85, 87, 86 to line 158 to operate the line-switch H. The impulses are then sent to operate the selector K and connector L. As soon as these have been delivered, the arm 92 separates springs 86, 87, and closes springs 87, 88, 89, thus bridging the relay 81 and magnet 82 across the line. The relay 81 holds the springs 87, 88, 89 in contact after the arm 92 has passed on and allowed the springs 86, 87 to engage. If the called subscriber answers, the direction of the line current is reversed as described in the prior Specification, the magnet 82 being energized to give a bell or other signal. The calling subscriber then removes his receiver, the contact 101 not being broken until the line circuit is made through the receiver. If the called subscriber is busy, the relay 272 energizes the relay 97, which opens the line circuit sufficiently long to de-energize the relay 81, thus permanently opening the line circuit so as to release the connexion, and simultaneously giving a signal to the calling subscriber. The relay 97 may be formed as a slowrelease relay or may be provided with a dashpot retarding-device.