Patent GB-139000-A (GB)
Abstract: 139,000. Automatic Telephone Manufacturing Co., and Friendly, H. M. Feb. 20. 1919. Automatic and semi-automatic exchange systems.-Relates to systems of the kind described in Specification 116,716, in which a connexion with a called party can be transferred to a third party by either the calling or called party, without first releasing the original connexion. The several features of the invention are indicated diagrammatically in Fig. 1, which shows a private branch exchange system wherein a calling- party A can extend a call through a selector A<1> and one of the selectors B' - - E<1> at the central exchange to a pair of interlinked connectors, such as G', H', J<1>, K<1> at the branch exchange. Thus, in the arrangement shown in connexion with the interlinked connectors G', a call to party B" is made direct through the switches A<1>, B<1>, G<1>, whereas a call to party K<11> is received at an operator's position R<1>, who then extends the call to party K<11>. Either party A or B" (or K<11>) can transfer the call to a party C". While all calls from the main exchange to party K<11> are intercepted by the operator R<1>, local calls and transferred exchange calls are received directly by the party K". In the arrangement shown in connexion with the connector H<1>, all calls coming in to the branch exchange are received at L<1> by an operator, who enquires the local number desired and operates the connector H' to select this line. In the arrangement shown in connexion with the .connectors J<1>, the operator's position N<1> is connected to bank contacts in the first level of one of the interlinked connectors, the circuit arrangements being such that, when a call is received from the main exchange, the wipers of the connector move automatically to the contacts of the operator's circuit. In the arrangement shown at the bottom of Fig. 1, calls are received at the branch exchange by a pair of interlinked groupselectors K<1>, which extend the connexion through connectors M' or M<11> to the wanted party H" or I". These four arrangements will be described in turn. First arrangement in which calls from the main exchange to certain parties are intercepted at the operator's position R<1>, Fig. 1. The terminals of these parties in the connector contact banks are connected to the equipment shown in Fig. 5, the operator's cord-circuit being shown in Fig. 5<A>. Before considering these circuits, it is necessary to describe the operation of the interlinked connector switches, shown in Figs. 2 and 3, for an ordinary call. The switch shown in Fig. 2, termed the " major " connector, is interconnected with the " interlinked " connector, Fig. 3, in such a way that the " major " connector is operated to select the party first called, and the " interlinked " connector is operated by either the calling or called party to select a third party. Each connector is provided with a relay adapted to operate as a second line relay in response to impulses transmitted thereto by the called party to set the wipers of the other connector on the terminals of a third or fourth party. In this first arrangement, the dotted connexions to the conductors r<2> - - w<2> are to be regarded as permanent, and the extensions of these conductors r<3>- - w<3>, Fig. 3, should be neglected. Operation of " major connector, Fig. 2, to select first party. When the junction b<3>, c<3>, Fig. 3, is taken into use at the main exchange, the line relay A<2>, Fig. 2, is energized over the springs of the reversing-relay Q<2> and closes the circuit of the usual slow-release relay B<2>. The first set of impulses is repeated by the relay A<2> over leads y<2>, z<2>, (which in this arrangement are assumed to be connected) to relay C<2> and the vertical magnet V<2>. The relay C<2> energizes the private magnet N<2>, so that when the impulses cease, the sideswitch arms 21, 22 are moved into their second position. The final set of impulses is repeated by relay A<2> over relay C<2> and armature c<22> of relay E<2> to the rotary magnet R<2>, which moves the wipers to the terminals of the selected line. Busy test and release. If the wanted line is busy, the connector operates as described in the next paragraph but two, and is released when the calling-subscriber replaces his receiver. Ringing-current. If the wanted line is free, the side switch passes into its third position, energizing relay H<2>, which connects the ringing- generator GN<21> to the wanted line, the circuit including the cut-off relay F<2>, which is energized when the subscriber replies, and completes the speaking circuit shown in thick lines. The ringing-current in one winding of relay F<2> induces in the other winding a current which passes to the calling-line. The wire aa<2> is earthed at the off-normal springs ON on the first vertical movement of the shaft to start the ringing and busy signal generator. Supply of microphone current; metering. The calling-line is fed through the relay A<2>, and the called line through relay K<2>, which energizes a slow-release relay J<2>, which in turn energizes a self-locking relay Q<2> to reverse the current in the calling-line for metering or supervisory purposes. Operation of connector to select the first free line of a group. An additional test wiper A<12> cooperating with the test wiper B" is used, and the test terminals of single lines and of the last line of a group are joined together, whereas the contacts of other lines of a group are not joined. If the selected line is a busy single line, the wipers A<12>, B<12> each engage earthed terminals, and the private magnet N<2> is energized over wiper B<12>, thereby locking the side switch in its second position, whilst the relay E<2> is energized over wiper A<12> and completes a locking-circuit for itself and the private magnet N<2>, at the same time connecting the busy signal transformer BB to the calling-line. If the selected line is the first of a group of lines and is busy, the private magnet N<2> alone is energized over wiper B<12>, locking the side switch in its second position, and a circuit is completed, when relay C<2> de-energizes, for the rotary magnet R<2> over armatures c<22>, n<22>, d<21>, c<22>. The magnet R<2> moves the wipers on one step and energizes a relay D<2>, which opens the circuit of magnet R<2>. The magnet R<2> and relay D<2> thus energize alternately until an idle line is found, whereupon the private magnet N<2> deenergizes, or until the wiper A<12> engages the earthed terminal of the engaged last line of the group, whereupon relay E<2> is energized as in the case of an engaged single line, and gives a busy signal to the calling-line. Normal release after conversation. If the calling-subscriber alone replaces his receiver, the release magnet RL<2> is not energized, as its circuit is opened by relay J<2> under the control of the called line. When the called subscriber hangs up, relay K<2> closes the circuit of a slow-release relav P<2>. the circuit being opened as soon as relay J<2> de-energizes. During the time that relay P<2> remains energized after relay J<2> has de-energized. the release magnet RL<2> is energized over armature j<24>, off-normal springs ON, front contact of armature p<22> of relay P<2>, relay G<2>, and armature j<22>, to earth. The relay G<2> effects the release of the interlinked connector in circumstances described later. Transfer of call to third party by called party. This can be effected by the caled party operating his dial in the usual manner without replacing his receiver. The side switch 21, 22 being in its third position, the first and second sets of selecting-impulses are repeated by the relay K<2> over the armatures k<22>, j<25>, h<26>, wires k<2>, k<3>, Fig. 3, slow-release relay C<3>, to the vertical and rotary magnets V<3>, R<3> of the interlinked connector, the wipers of which are thus moved to the terminals of the third party. During the adjustment of the connector, relay C<3> closes a circuit for relay L<2>, Fig. 2, which locks up and opens the line circuit so that the calling-party is not disturbed by the selecting-impulses. The selected line is tested and, if idle, supplied with ringing-current in the same way as in the major connector, the relays E<3>, F<3>, H<3>, Fig. 3, corresponding to the relays E<2>, F<2>, H<2>, Fig. 2. Microphone current is supplied to the calling-line through relay A<2>, Fig. 2, and to the third party through relay K<3>, Fig. 3. The major connector, Fig. 2, is released, as previously described, when the party first called hangs up, or, in a modification, automatically when the third party replies. The third party can transfer the call to a fourth party by operating the major connector in a similar manner. Transfer of call to third party by calling-party. This can be effected by the calling-party operating his dial without replacing his receiver. The side switch 21, 22 'being in its third position, the selecting-impulses are repeated by the relay A<2> over armatures a<21>, b<22>, h<26> and wires k<2>, k<3> to vertical and rotary magnets V<3>, R<3>, Fig. 3, as before. Operator's circuits, Figs. 5 and 5<A>, for intercepting incoming calls to certain lines. The circuit shown in Fig. 5 is arranged at R', Fig. 1, between the party K<11> and his terminals in the major connector G<1>, the operator's cord terminating in plugs P<5>, P<15> being shown in Fig. 5<A>. The circuit shown in Fig. 5 is such that, while calls from the main exchange are intercepted by the operator, local calls and transferred exchange calls are received directly by the party K<11>. This differentiation is effected by the use of ringing- generators GN<21>, GN<22>, Fig. 2, of different frequencies and of a tuned relay A<5>, Fig. 5, which responds only to current from the generator GN<21>, whilst the bell at station K<1> responds only to current from generator GN<22>. Local calls are made through lo