143,842. Automatic Telephone Manufacturing Co., (Assignees of Homrighous, J. H.). May 28, 1919, [Convention date]. Automatic and semi-automatic exchange systems.-A selector trunk is accessible from several sets of terminals, such as the jacks J, J<1>, J<2> &c., Fig. 1, of a manual board, or the bank terminals in one or several levels of a group selector F, Fig. 3, and an impulse-sending device D, Fig. 1, or D<1>, Fig. 3, associated with the selector, is arranged to transmit to the selector E a number of impulses determined by the jack or set of bank terminals over which the selector is taken into use. Thus an operator may effect the first stage in the selection of a subscriber on a distant automatic exchange by the choice of the jack into which she plugs. Semi-automatic working. The insertion of a calling-plug P in the jack J<1>, say, closes a circuit including relay 2 in the cord-circuit, sleeve of plug, relay 7, contacts 4, 15, and impulse relay 20 of the selector. Relay 20 energizes the usual slow-release relay 21, and bridges a resistance 25 and the lower winding of relay 26 across the condenser 24. Relay 7 earths the second contact in the path of the wiper 46 of the impulse-sender D, and causes a relay 9 to close the circuit of the stepping-magnet 12 which moves the wiper 46 over the contacts 47, until the contact earthed by the relay 7 is reached, whereupon the relay 10 energizes, lights the lamp L<2>, disconnects the stepping-magnet 12, and short-circuits the relay 7 over contact 40. At each operation of the stepping-magnet 12, the relay 13 is energized and opens the circuit of the impulse-relay 20, which repeats the impulses through the series relay 32 to the vertical magnet 33 in the usual way. The selector wipers are thus raised to a level determined by which contact 47 is earthed, that is by the jack J' into which the plug is inserted. When the selecting-impulses cease, the wipers are rotated in known manner to find an idle trunk to the distant exchange, whereupon the switching- relay 67 is energized and extends the call to the second exchange. The operator, noticing lamp L<2> glowing, depresses key K to cut in her impulse-sender CD by which she completes the selection of the wanted line, the selecting-impulses being repeated by relay 20 at contact 27. When the called subscriber replies, the current over the trunk is reversed so that the two windings of relay 26 assist each other, relay 26 energizing relay 75, which by substituting relay 21 for the impulse relay 20 increases the resistance in series with relay 2, Fig. 1, so that this relay is de-energized and cuts out the lamp L. The connexion is released on the withdrawal of the plug P. By depressing her ringing key, the operator may energize a relay 120, which earths the wiper 53 so as to operate certain devices at the distant exchange prior to the actual establishment of the connexion. Full automatic working. The selector trunk E may be accessible from the various levels of a selector switch F, Fig. 3, the impulse-sender D' transmitting to the selector a number of impulses determined by which of the contacts, engaged by wiper 46', is earthed by relays, such as 104, 105, that is according to the level or set of terminals over which the selector is taken into use. The operation is similar to that of the system previously described, relays 9<1>, 10<1>, 12<1>, 13<1>, 20<1> corresponding to relays 9, 10, 12, 13, 20 in Figs. 1 and 2.