Patent GB-513507-A (GB)
Title: Improvements in automatic switches for use in telephone or like systems
IPC: H04Q3/00
Filed: 1938-04-12
Abstract: 513,507. Automatic exchange systems and switches. ASSOCIATED ELECTRIC LABORATORIES, Inc. April 12, 1938, No. 11234. Convention date, May 3, 1937. [Class 40 (iv)] In a cross-bar switch, both sets of bars partially operate the contacts in their respective rows, the contacts at the intersection being fully operated. Selection in both directions is controlled by a permanently associated stepby-step switch so that the controlling circuits when the switch acts as a group or final selector resemble those of a Strowger-type switch acting in similar capacities. Switch construction. Operation of one of the vertical magnets 44-48 draws down the corresponding one of the bars 49-53 to depress all the upper contacts in a particular vertical row. When the switch is to act as a group selector, circuits are made by this operation over springs (not shown) co-operating with all the test contacts to enable a marker to hunt for an idle outlet in the selected group. Operation of one of the horizontal magnets 18-22 raises the corresponding one of the bars 28-32 to raise the lower contacts in its horizontal row. Upper and lower contacts are thus brought into engagement at the intersection of the operated bars. The horizontal bars may be actuated by two magnets in parallel, one at each end. Group selector, Fig. 7. Line and release relays 200, 210 pull up when the switch is seized and the first digit is repeated to the marker magnet 205. Relays 220, 230 are energized throughout the digit and then fall in succession. A temporary circuit is thus made for the selected vertical magnet, e.g., 240, which locks up, and a self-interrupting circuit is then made for the marker magnet 205. The vertical magnet connects the test wires of all final selectors in the selected group to the bank 215 of the marker over springs such as 243, 244, and, when an idle one is reached, polarized relay, 250 pulls up quickly over this wiper, stops the marker and energizes the selected horizontal magnet, e.g., 260, which locks up 250, interrupts its energizing circuit, but holds over its lower winding which was energized initially to make it quick-acting. It also releases 200, 210, whereupon the marker goes home. The energizing ground for the horizontal magnets passes over contact 261 and a chain of similar contacts, and the marker is thus unable to operate other magnets during its restoration. Final selector, Fig. 8. The' marker 307 is set by the tens digit in the same way as that of the group selector with the help of line and release relays 300, 310 and a pair of sluggish dialling relays 320, 330. The relapse of 320 energizes the selected vertical magnet over the tens wiper 315 of the marker, and that of 330 allows a two-step relay 340, which it energized partially at the beginning of the digit, to pull up all its armatures. At the same time a selfinterrupting circuit is made to send the marker home. It is then set in a similar manner by the units digit but, since 340 is energized, the relapse of 320 this time energizes a horizontal magnet over the units wiper 316. On the subsequent relapse of 330 the marker again goes home. Busy test and signal and control of ringing current. In the interval between the relapse of 320, 330, busy relay 350 is connected to the private wire 137 and, if the wanted subscriber is busy, locks up and sends back busy tone. If 350 is not energized, the relapse of 330 connects 370 to the private wire and ringing current is then sent out over the ring-trip relay 360 which completes the connection when the subscriber replies. Release. No effect is produced when the called party hangs up. When the calling party hangs up, 300, 310 fall back and the switch magnets and relays are released. To avoid trouble if release should cause 307 to step on, an alternative homing circuit is provided for it in the normal condition of the circuits.