175,260. Automatic Telephone Manufacturing Co., Ltd., (Assignees of Nelson, M. L.). Feb. 9, 1921, [Convention date]. Semi-automatic exchange systems; impulse transmitters.-An operator's sending-equipment comprises a single row of keys 1 - - 0, Fig. 2, a sending-switch S, Fig. 5, and a relay register for each digit of the wanted number, of which the first and second digit registers are shown in Figs. 6 and 7. The successive momentary depression of the keys corresponding to the wanted number causes the energization of corresponding relays of the series 271 - - 270, Fig. 6, 321 - - 320, Fig. 7, &c. Each register selects a marking circuit for the switch S and prepares the next register for control by the keys. The registers also light lamps in a number-indicator to enable the operator to check the number she has recorded. The switch S moves from normal to normal for each digit, sending impulses to line in step with its movement, but the transmission of impulses is cut off when the switch reaches the marking circuit selected by the corresponding register. The sending-equipment is described as for use by a B operator at an automatic exchange in extending calls from a manual exchange. Three or four senders may be provided for a large group of incoming trunks, relays 45, 46, &c., Fig. 2, controlled by keys K<1>, K<2>, &c. being provided for connecting any sender to any trunk. The B-operator as she receives a wanted number from the A-operator writes it down on the keys of an idle sender, then assigns an idle selector trunk 30, 31 to the A-operator over the order-wire 20, 21, and presses the key K<1> to connect the sender to the outgoing trunk, after which the operations are completed automatically and the sending-equipment releases itself. Registration of the wanted number. The first depression of a key 1 - - 0, Fig. 2, energizes a corresponding relay 271 - - 270, Fig. 6, which, upon the release of the key locks itself to the wire 226 in series with a relay 252 which energizes relays 253, 254 to disconnect relays 271 - - 270 from the key-wires and energizes relays 304, 305, Fig. 7, to connect the key-wires to relays 321 - - 320. The second depression of a key therefore energizes a corresponding relay 321 - - 320, which, upon the release of the key, locks itself in series with a relay 303, which deenergizes relays 304, 305 and energizes corresponding relays in the next register to connect the next register to the key-wires, and so on. The relays 252, Fig. 6, 303 ,Fig. 7, &c. each connect ground to a circuit 223 to light a busy lamp L<4>, Fig. 2, and to prepare a locking-circuit for the relay 45. Tell-tale number-indicator; wiping out erroneous registrations. The register relays close circuits such as 284, Fig. 6, 335, Fig. 7, for lighting lamps corresponding to the registered number. If an error has been made the operator can wipe the number out by depressing a key R to energize a relay 203, which onens the circuit 226 to unlock all the energized relays in the registers. Connection of the sending-equipment to the assigned trunk. As soon as the lamp L<3> is lit, indicating that the A-operator has plugged into the trunk 30, 31, the B-operator presses the key K<1> to energize the relay 45, which locks itself to the wire 223, energizes the self-locking relay 44, connects the sender wires 221, 222 to the outgoing trunk 60, 61, and connects the grounded wire 223 to the wire 224 to energize relays 204, 205, Fig. 5. The relay 204 disconnects ground from the wire 228 to extinguish the numberindicator. Impulse transmission. The grounding of the wire 224 also completes the circuit of a relay 202, Fig. 5, in series with an interrupter 298, so as intermittently to energize the stepping magnet 206 of the switch S. At the first de-energization of the magnet 206 the switch S is moved from normal and energizes a relay 201, which opens a contact 212 bridging the wires 221, 222 in the circuit of the outgoing trunk, so that each subsequent energization of the relay 202 causes an interruption of the trunk circuit at contact 214. When the wiper 208 arrives on the marking circuit closed by the first digit register it energizes a relay 200, which locks itself, open-circuits the relay 202 to prevent the further transmission of impulses, energizes a relay 252, Fig. 6, over the wire 227, and closes an off-normal self-interrupting circuit for the magnet 206 to step the switch S at high speed to its next normal position, whereupon the relays 201, 200 successively relapse. The de-energization of the relay 201 disconnects ground from the wire 227 so that a relay 250, Fig. 6, becomes locked in series with the relay 251. The relay 250 disconnects ground from the feed-wire 288 of the first-digit marking circuits and grounds the feed wire 286 of the second-digit marking circuits. The de-energization of the relay 200 restores the circuit of the impulse relay 202 to initiate the second-digit impulse transmission. The second digit is controlled in the same manner as the first, after which the relay 301, Fig. 7, is energized in the same way as relay 250, Fig. 6, to disconnect ground from the feed-wire 388 of the seconddigit marking circuits and to ground the feedwire 386 of the third-digit marking circuits. The third and fourth digits are transmitted in the same way. It will be noted that the digits are separated by intervals corresponding to the sum of the periods of release of the sluggish relays 201, 200. Release of the sending-equipment. When all the digits have been transmitted, the ground connection of the wire 223 in all the registers has been removed by the energization of the relays 250, Fig. 6, 301, Fig. 7, &c. The ungrounding of the wire 223 unlocks the relay 45, Fig. 2, which disconnects the sender and completes the talking circuit. The wire 224 derived its ground potential from the wire 223, so that the relays 204, 205, Fig. 5, become successively de-energized, with the result that the wire 226 is momentarily open-circuited to unlock all the energized relays in the registers. Supervisory signals and release. The revensal of current in the trunk 60, 61 when the called subscriber replies, energizes an electropolarized relay 42, which reduces the bridge resistance of the incoming trunk 30, 31 to energize a supervisory relay in the A-operator's cord circuit. Conversely, when the called subscriber disconnects himself the supervisory relay is de-energized. When the A-operator releases the trunk 30, 31 the de-energization of the relay 40 extinguishes the lamp L' and unlocks the relay 44, which opens the trunk 60, 61 so as to release the automatic connection.