Patent GB-191121260-A (GB)
Title: Improvements in Switching Apparatus for Interconnecting the Lines of a Semi-automatic Telephone System.
IPC: B43K29/20
Filed: 1911-09-26
Granted: 1912-10-28
Abstract: 21,260. Western Electric Co., [Telephon Apparat. Fabrik E. Zwietusch & Co.]. Sept. 26. Semi - automatic exchange systems ; coin - freed systems; metering systems.-A system is described in which a calling line is connected by means of call-finders to an idle selector trunk normally associated with a particular operator, with whom, if idle, connexion is obtained. The operator then selects the desired line by means of 200-point selectors, " translation " being necessary as explained in the preceding abridgment- 21,259/11. The principal features claimed are as follows-(1). A calling line is connected with one of a number of operators, if one is idle, but if none of them is idle is indicated before one of them by a visual signal individual to the call. (2). A calling line is indicated by a visual signal before a particular operator, and is automatically connected to such operator if she is idle, but, if not, is connected to another operator. (3). The idle operator is selected by means of a sequence switch individual to the selector trunk, and the same sequence switch serves to find an idle controlling - equipment belonging to that operator. (4). The operator is provided with a single keyboard and two controlling-equipments, which register the number recorded on the keyboard, and then control the operation of the selectors, an idle controlling-equipment being automatically connected to the selector trunk and to the keyboard. (5). The selector trunk is connected by a single automatic switch to the operator's speaking set independently of its connexion to the controlling-equipment, so that the speaking set can be disconnected automatically as soon as the keyboard has been set, leaving the operator free to attend to a further call, while the selection of the wanted subscriber is proceeding under the control of the registering-equipment. The controlling- equipment is disconnected as soon as the final selector has been brought to the terminals of the wanted line, before the line is tested or supplied with ringing-current. Other features of the system described are claimed in Specifications 20,946/12 and 20,947/12. Construction of selectors, call-finders, and sequence switches. The construction of these switches is identical with those referred to in the preceding Abridgment No. 21,259/11, and the same convention is used to indicate the positions of the sequence switches in which their respective contacts are closed. Operator's controlling-equipment. Each operator is provided with two equipments fcr controlling the operation of the selectors, a single keyboard being common to the two. The keyboard, Fig. 6, comprises ten keys each for the thousands, hundreds, tens, and units digits, the keys being locked in the depressed position by the magnets 290 ... 293. Each controlling-equipment, Fig. 5, comprises four registers, which structurally resemble sequence switches and are represented by their clutch magnets 160 ... 163, and the contactsprings above and below these magnets, the springs individual to each register being indicated by the dotted lines. The four sets of fixed contacts of the upper sets of springs are connected respectively to the four sets of digit keys, Fig. 6, in such a way that when the registers are set in motion they rotate until the contacts, which are earthed by the depressed keys, are closed, thus energizing the relays 170 ... 173, and opening the circuits of the clutch magnets 160 ... 163. The registers thus record the number set up on the keyboard, which is then released and can be used in connexion with the second controlling equipment. As the two-thousand line system described uses 200-point selectors and connectors, translation is necessary, and is effected by the lower sets of springs of the registers, which are connected to twenty pairs of impulse-counting relays 179, 180. The successive levels of the group selectors lead to connectors serving the lines 0-199, 200-399, 400-599, and so on. Thus to call lines in the first thousand (0-999) the first five levels are used, and to call lines in the second thousand (1000-1999) the sixth to the tenth levels are used, that is to say the brush chooser must move through five more steps to select a line in the second thousand than in the first thousand. To this end, the hundreds register 161 has two sets of contacts 183 ... 187, 192-196, and one or other of these sets is made operative according to the position of the spring 191 on the thousands register, which closes its upper or lower contact according to whether the thousands digit of the wanted line is odd or even. In the connectors, the first ten sets of contacts in each of the ten levels are connected to the corresponding subscribers in the even hundreds, and the second ten sets to subscribers in the odd hundreds. The units selection consequently depends upon the hundreds digit of the wanted line, it being sometimes necessary to move through as many as twenty steps. To this end the units register 163 has two sets of contacts 183<b> ... 187<b>, 192<b> ... 196<b>, and one or other of these sets is made operative according to the position of the spring 197 on the hundreds register, which closes its upper or lower contact according to whether the hundreds digit is odd or even. The operation of the controlling-equipment is governed by a sequence switch represented by its clutch magnet 505. Lamps 297, 299, 350 indicate the progress of the selecting- operations. General operation of the system. When a subscriber removes his receiver, all the idle call-finders, 100, Fig. 1, serving his group, hunt for the calling line, and thereafter a further set of finder switches, 200, Fig. 2, permanently associated with selector trunks, hunt for the operative call-finder. As soon as the second line-finder has established connexion with the calling line, a group sequence switch 305, Fig. 2, and a position sequence switch 205, of each of which there is one for each selector trunk, connect the telephone set of the home operator to the calling line, or, if this operator is busy, connect the telephone set of the operator to the left, if idle, to the calling line. The position sequence switch 305, having selected the idle operator, next determines which of the two controlling. equipments A or B, Fig. 5, is to be taken for use. The operator then ascertains the connexion desired, and writes it down upon her keyboard, Fig. 6, thus registering it upon the registers of the selected controlling-equipment shown in Fig. 5. As soon as this registration is complete, the operator's speaking set is disconnected from the calling line, and her keyboard from the controlling-equipment, so that she is free to attend to another call while the selection of the wanted subscriber is proceeding under the control of the first equipment. As soon as the wipers of the connexion reach the selected line, and before the application of ringing-current, &c., the controlling- equipment is released from the connexion and can be taken into use to establish a further connexion. When the subscribers replace their receivers, supervisory lamps light up, and the operator releases the connexion by depressing a special key, at the same time metering the call, or if a coin-freed station is the calling line, collecting the coin. The detailed operation of the system is described in the following paragraphs. First call-finder. When a subscriber removes his receiver, his line relay 51, Fig. 1, puts a selectable potential on his terminals 104 in the callfinders of his group, and energizes the common pilot relay 52, which closes circuits for all the idle callfinders over contacts 55, 56, and power magnet 106. The test-wiper 104<a> is earthed through the relays 108, 107, the latter relay being short-circuited by the interrupter contact 109 except when the finder wipers are accurately centered on the line terminals. As soon as a call-finder finds the calling line, the relay 108 energizes, and, by closing a circuit through its low-resistance winding, renders the calling line non-selectable to other finders. When the wipers are accurately centered, the relay 107 energizes and (1) disconnects the magnet 106, (2) energizes the holding-magnet 110, and (3) energizes the clutch magnet 105 so that the sequence switch moves into its 4th position. In the 2nd position, the cut off relay 62 is energized over contacts 61, 60, thus connecting the calling line to the wipers 101<a>, 102<a>, and reducing the potential an the test lead so as to mark it engaged. The sequence switch 105 remains in its 4th position during the operation of the second call-finder, after which it is moved into its 5th or talking position. Second call-finder. In the 4th position of the sequence switch 105, Fig. 1, the relay 107 is connected to the terminal 204, Fig. 2, and the contact 63 closes the circuits of the motor magnets 209 of all the idle second call-finders, the test wipers of which are connected to relays 208, 207, corresponding to the relays 108, 107, Fig. 1. As soon as the calling line is found, the relays 207, 208 are energized, and the relay 207 disconnects the magnet 209, energizes the holding magnet 210, and moves the group sequence switch 205 into its 2nd position. During this movement, an impulse is sent through the back contact of relay 67, key 68, relay 199, contacts 69, 203 to the clutch magnet 105, Fig. 1, thus moving the first finder sequence switch to its 5th or talking position. The circuit of relays 207, 208, 107 remains closed until the connexion is released. Selection of idle operator. Each selector trunk is normally associated with a certain operator, with whom, if idle, connexion is made. If, however, the normal or home operator is busy, connexion is made to the operator on her left. In either case, or if both operators are busy, a lamp 95, Fig. 2, individual to the selector trunk, lights up, indicating that a call requires attention. As the group