Patent GB-296044-A (GB)
Title: Improvements in automatic or semi-automatic telephone systems
IPC: H04Q3/00
Filed: 1927-05-24
Abstract: 296,044. Standard Telephones & Cables, Ltd., (Deakin, G., and Polinkowsky, L.). May 24, 1927. Automatic exchange systems. - A rotary connector has individual lines and/or groups of lines connected to its contact bank, and the cut-off relays of the first and last lines of groups are shunted by a resistance in order to give the difference in operation necessary when a P.B.X., for instance, is called. The test relay is arranged to operate momentarily on a busy first line of a group in order to initiate circuit changes so that the switch hunts over the lines of the group, and if all the lines are busy a similar operation takes place and the busy signal is sent back. Call to single line. When the final selector is seized relay Flr operates over cam I, the fundamental circuit, and cam H, and sequence switch R is then moved to second position over cam B. The trip-spindle magnet P2 is now energized over cam C to select the required level, revertive impulses being sent back by interrupter INT2, and relay Flr is then released, switch R moving to position 4. In passing position 4¥, Flr energizes over the off-normal contact X1 and locks over the previous loop. When the register opens the loop, Flr de-energizes, and R moves to position 6. Flr again energizes in R5¢ and locks. The brush-rotating magnet PI is now operated, INT1 sending back revertive impulses, and the required line is found when Flr de-energizes and R moves to R9¢. Completion of connection. Relay Ftr energizes (subscribers cut-off relay COR, brush c, Ftr, armature ofPBr, E, earth) at R6¥, and locks up over its front contact. Flr energizes momentarily only at R8¥, so that R moves on to R11“. At R10 the short-circuit round relay Pbr is removed, and Ftr, Pbr then energize in series. When Pbr is shorted at R11“, Fto remains energized over its armature, so that Flr only pulls up momentarily at R10“, R12 over XI, and R passes positions 11“, 12¢. Pbr is cut out, R12, Ftr being held over its armature. At R13¢, Flr energizes over XI and locks over cam G to the preceding switch, so that R steps past position 14 to the talking position 15. Release. When the calling subscriber hangs up relay Flr releases, and R moves to R16, and at 15# Flr energizes and locks up over the called loop. On the called subscriber hanging up, R moves to R17, relay Flr energizing again from 16¥-17 so that P2 energizes over C and returns the trip spindle to normal. Ground on off-normal contact X1 is taken off so that Flr releases and R moves to R18, when PI energizes over cam K and returns the brushes to normal, closing normal contact X2 so that Flr de-energizes and R returns to normal. Line busy. Relay Ftr is not energized at R6¥ as there is short-circuiting earth on brush c so that R stops at R9¢, a busy signal being sent back by ground over cam L to the a wire, and battery on the test wire over Flr. Call to P.B.X. If the first line is idle it is seized as above, but if busy, Ftr still energizes over the shunting resistance 800, so that R passes R9¢. Ftr de-energizes, but Pbr energizes at R10“ to earth at E, and Flr locks up when energized at R10“, so that R stops at R11“. P1 now operates over cam C and Pbr de-energizes when the first line is left since there is a controlling earth on busy intermediate lines. When an idle line is found, Ftr energizes, releasing Flr, so that the brush carriage stops, and R moves to R15 as for an individual line. All P.B.X. lines busy. Ftr will energize on the last line, and R will step on. On leaving R11“, the locking circuit of Ftr is opened, and Ftr is in series with Pbr so that the former deenergizes. Flr therefore locks up at R12, the sequence switch stops at R12¢ and a busy signal is sent back by ground to the a wire over cam H, and battery on the test wire.