157,233. Ges. fiir Electromechanische Telephonapparate. June 4, 1914, [Convention date]. Automatic and semi-automatic exchange systems; metering systems.-In establishing a talking connection, two transitorily used switches are employed, one of which hunts to find the calling line, whilst the other is set by numerical impulses upon the contacts of the wanted line. These two switches cause two simple talking connection switches to hunt for the calling and called lines, and are then released so as to be available for establishing further connections. Three arrangements are described for carrying out the invention. In the first arrangement, Fig. 1 the transitorily used switches S1, S2, and the talking connection switches V1, V2, V3 are adapted to be set either on calling or called lines. On a subscriber T1 removing his receiver to establish connection with another subscriber T3, an idle switch S1 hunts for the calling line and extends the connection through its associated trunk-finder VS1 to a free selector-finder WS1, which hunts for an idle trunk t3 connected by a trunk-finder VS2 to a free switch S2. The second transitorily used switch S2 is set on the contacts of the wanted line T3 by the selecting impulses. The setting of the switches S1, S2, causes selective potentials to be placed on the corresponding contacts of the talking connection switches. On the operation of the selector-finder WS1, the switch VI associated therewith, hunts to find the calling line, whilst after the setting of the second switch S2, the talking connection switch V3 associated with the trunk t3 hunts to find the wanted line. The transitorily used switches S1, S2, are now thrown out of operation, and the talking connection maintained through VI, t1, WS1, t3, V3. According to a second arrangement, Fig. 6, two groups of transitorily used switches are provided, one for connecting the calling subscriber to unseized trunks and the other for selecting the wanted line. When a subscriber T1 calls T3 he is connected by a transitorily-used line finder S1 and its associated trunk finder VS2 to a trunk lg2 leading to an idle group selector GW2, which in response to the first series of impulses is stepped up to the level in which the trunks fl - f4 leading to the wanted group, terminate. A trunk f3 leading to an idle trunk l3 and an idle transitorily-used wanted line selector LW1, is then seized, and the remaining impulses set the selector LW1 upon the wanted line T3. The permanent talking connection switch V3, associated with the seized trunk l3, now sets itself upon the wanted line T3 marked by the transsitory switch LW1. When the calling line is extended to the trunk lg2, an intermediate finder ZV4, associated with an idle trunk l4, sets itself on the trunk lg2, and an associated talking connection switch V4 hunts to find the calling line T1 marked by the transitorily used switch S1. A permanent talking connection over V4, l4, ZV4, lg2, GW2, f3, 13, and V3 is now completed, and the transitorily used switches S1, LW1 are released. In a third arrangement, Fig. 5, two groups of both transitorily used switches and talking connection switches are used, one group of each kind for establishing connection with calling lines only, and the other group for extending to called lines only. When a subscriber T1 calls T4, connection is made through an idle pair of transitorily used switches S1, W1, switch S1 hunting for the calling line and selector W1 being set upon the wanted line. The associated trunk finder VS1 is connected to a free pair of talking connection switches V4, V<1>4, which hunt for the calling and called lines respectively, the switches S1, W1 being then released and connected to a free pair of talking connection switches by the trunk finder VS1. The operation of the first arrangement, Fig. 1, only is described in detail with reference to Figs. 2, 3, and 4, which should be placed side by side to form a single diagram. Preparation of connection over two transitorily used switches S1, S2. On removing the receiver T1 to make a call, the group relay GR is energized and a circuit is momentarily completed over the starting wire 87 for the driving magnet M of the first idle switch S1. which advances its wipers ore step. Movement of the off-normal switch 16 causes the magnet M to be energized by the interrupter 29, and the switch S1 continues to rotate until the wiper d1 of one of the sets of w:pers engages the earthed contact 31 of the calling line, and completes a circuit through the test relay 32, which locks up over its upper winding and closes circuits for the cut-off relay 4 and the relay 52. In order that the group relay GR is net reenergized by another calling subscriber before its armature 9 falls back, the relay 4 may be provided with a contact which closes a circuit through another group relay which in any case momentarily breaks the circuit of the group relay GR. The relay 52 locks up over the switch 16 and disconnects battery from the lower windings of the test relays 32, 45, so that when the switch S1 is returned to normal the test relays will not be re-energized if an earthed contact is engaged. The closure of the contacts 49, 50 of relay 4 results in the response of the starting relay 59 of a free selector-finder WS1 connected to the switch S1 over its associated trunk-finder VS1. The driving-magnet M1 is thereby energized and rotates the wipers a<3>, b<3>, c<3>, d<3> until the test wiper c<3> engages an idle trunk t<3> leading to a free transitory switch S2 through its associated trurk-finder VS2, when the stopping relay 73 is energized in series with the relay 14 of the idle switch S<2>. (Henceforth, for convenience in abridging, in describing circuits over switch WS3 and the operation of switch S2, reference is made to the switches WS1 and S1 shown in detail in the figures). The relay 73 opens the circuit of the driving magnet M1, whilst the relay 14 (a) establishes a locking circuit for itself over armatures 80<1> and 23, (b) energizes relay 93 of the selectorfinder WS3 associated with the seized trunk t3, (c) completes a dialling circuit through the impulse relay 118 of the second transitory switch S2, and (d) transfers starting wire 87 to the next transitory switch. Setting of second transitorily used switch S2 upon contacts of wanted line by numerical impulses. The circuit of the relay 118 is now interrupted by the " tens " impulses, and at each interruption the primary magnet ZM is energized, and steps round the wipers 137, 138 to select the particular set of wipers of the switch S2, having access to the wanted line. In the short pause which then ensues, relay 128, which was energized over the armature 84, is short-circuited and a momentary closure of the contacts 141, 142 energizes the relay 147, which locks itself over its upper armature and prepares a circuit through the driving magnet M. The "units" impulses de-energize the impulse relay 118, which completes the circuit of the driving magnet M and steps the wipers on to the contacts of the wanted line. Setting of talking connection switch V<1> on calling line. The energization of the starting relay 59 of the selector-finder WS1 completed a circuit through the driving magnet M2 of its associated talking connection switch VI. One of the contacts in each of the terminal banks of the transitory switches is connected by an identifying wire to a test contact in the corresponding terminal bank of the talking connection switches, there being a separate test contact in each bank of the talking connection switches for each transitory switch. When the wipers of the switch VI engage the calling line, the identifying relay 103 is energized over the identifying wire eK and wiper e4, locks itself over contacts 110, 111, and breaks the circuit of the driving-magnet M2. Setting of talking connection switch V3 on wanted line. After the calling subscriber has finished dialling the wanted number the relay 128, of the transitory switch S2 set on the wanted line, relapses, and if the wanted subscriber is free, the relays 45 and 155 are energized over the wiper c2 (if " tens " digit is 2). Both relays lock themselves up, relay 155 completing a circuit for the driving magnet M2 of the talking connection switch V3 connected to the transitory switch S2. (Hereafter the operation of switch V3 is described with reference to V1 of the diagrams.) The wipers of the switch V3 rotate until its identifying wiper e3 engages the contact on which a selective potential has been placed by the transitory switch S2, when the identifying relay will be energized and the driving magnet stopped. The circuit of the identifying relay includes an identifying wiper 170 of the trunkfinder VS2 associated with the switch S2 set on the wanted line, so that the identifying relay can only be energized if the wiper e3 engages a test contact connected to the transitory switch S2 associated with the trunk finder VS2. Movement. of trunk finders VS to idle trunks and release of transitorily used switches. On the response of the identifying relay of the switch V3 set on the wanted line, the starting relays 172 of both trunk finders VS1 and VS2 are energized and complete the circuit of driving magnets 184 through interrupters 183. The wipers of both finders are thereby rotated until an idle trunk is found, when the starting relays 172 are de-energized and the hunting action stopped. The response of the starting relays 172 breaks the locking circuits of the test relays of both transitory switches S1, S2 at contact 47 and both driving magnets M are energized over the interrupters 29 and off-normal switches 16 to return the transitory switches to normal. The energization of the starting relay 172 of the finder VS2 also breaks at 190 the circuit of the impulse relav 118 of the transitory switch set on the wanted line. Relay 133 is thereby short-circuited causing (1