Patent GB-1051670-A (GB)
IPC: H04Q3/00
Abstract: 1,051,670. Automatic exchange systems. WESTERN ELECTRIC CO. Inc. June 28, 1963 [June 28, 1962 (3)], No. 25761/63. Heading H4K. In an exchange system utilizing stages of ferreed switching matrices, each matrix has one end of all of its columns and rows connected to a common bus. Each ferreed is a remanent relay having two windings both of which must be simultaneously energized to operate the relay and either of which when energized alone releases the relay. One of the windings is connected in series with a row conductor of the matrix while the other winding is connected in series with a column conductor. The energizing pulses must be accurately synchronized otherwise if the trailing edge of one pulse persists after that of the other, the just-operated cross-point will be inadvertently released. However, by means of the common bus, a marking pulse 4 applied to say column 06C will pass through a series circuit comprising the column windings W2 of 09CZ, 09CY, 09CX, bus 010 and for example the row windings W1 of 09AX, 09BX, 09CX to ground at 07X whereby irrespective of the length of the pulse relay 09CX is operated. Since only one winding of the other relays mentioned is energized these relays, if already operated, will release. Trunking.-The switching network comprises N stages of m matrices each. The linking is such that any outlet, e.g. 07X, of a first stage matrix has access to one matrix only, e.g. N-0 of the last stage. The network is non-degenerate and full-availability between inlets and outlets exists. Setting up a connection.-The speech paths completed by operation of a selection of ferreeds are not shown. Each inlet A, B, C of the network is supervised by a cut-off bipolar ferreed switch 08 whose contacts normally connect a scanning circuit (not shown) to the test terminals (not shown) associated with each inlet. When it is determined that a path between inlet C of matrix 0-0 and outlet C of matrix N-0 is to be set up, the selectors 01 and N1 ground leads 013 and N13 in order to operate matrix selection relays 012 and N12 which close their contacts 011 and N11 so as to cause continuity in the common buses 010 and N10 of the chosen matrices only. Selector 01, then applies a pulse 4 via column 06C, bus 010, row 07X, link 51, row N7X, bus N10, column N6C to ground in selector N1 whereby relays 09CX and N9CX come up and any others in the series circuit release. Ferreed switch 08C operates in this circuit so as to disconnect the scanner from the test terminal of inlet C. Release.-In order to release a. connection it is only necessary to release the operated relay in the first stage since the other relays are released automatically whenever a new connection is set up. Again selector 01 operates relay 012 by grounding 013 but in this case it grounds column 06C instead of pulsing it. A further selector 02 pulses lead 014 whereby 09CX drops-back and 08C reconnects the scanner to the inlet. Testing.-(1) Remove supervision from an idle inlet may be required and this is effected by pulsing, e.g. column 06C and grounding bus 010 by means of selector 02 whereby 08C is energized so as to disconnect the scanner from the inlet without any of the column relays 09CX to 09CZ being operated. (2) Test supervision of a particular idle inlet from a particular outlet without disconnecting the scanner may be required and this is achieved by grounding, e.g. column 06C and pulsing column N6C whereby relays N9CX and 09CX come up but 08C is not affected. Network test, during maintenance routines or in the event of trouble, involves a selective test of all the network paths except those through the first stage matrices and is effected by applying ground to the selected outlet column and pulsing lead 014 by means of selector 02. Scanning of the inlets is unaffected during this test.