Patent GB-899140-A (GB)
Title: Improvements in or relating to circuit arrangements for telephone installations in which switching selectors are arranged to be set by means of marking devices
IPC: H04Q3/42
Filed: 1959-02-13
Abstract: 899,140. Automatic exchange systems. SIEMENS & HALSKE A.G. Feb. 13, 1959 [March 10, 1958 (2)], No. 5129/59. Class 40 (4). In a system in which a marker is common to a plurality of selectors of a switching stage and is associated therewith over a hunting switch, the test circuit for stopping the hunting switch passes over the same wire as is eventually used for passing the digits to the marker from a recorder at the beginning of the switch train. Operation of recorder.-Figs.. 1a, 1b.-The feed-bridge circuit SpUe is seized over the c-wire relays A, C coming up over this wire, the former then being maintained by the subscriber's loop. Relay A connects up dial tone WZ and relay C sends forward a seizing signal over the c-wire. Impulses step the magnet EM of a storage device and bring up relay V which is followed by K which disconnects the dialling tone. At the end of the first impulse magnet MM of the device also operates and holds. At the end of the impulse train V releases followed by magnet MM. The storage device consists of a disc rotatable by the pulsing of EM, and carrying segments which are depressed and held below as insulating ring when MM is operated. Thus the segment corresponding to the first pulse of a train remains in the raised position and the remaining segments are depressed. Further digits are stored in the same manner, so that the registration consists of consecutive groups of segments of number equal to the value of the respective digits, the first segment for each digit being raised. The storage device carries a wiper pk which is carried round from a normal position by the disc and in doing so operates off-normal contacts so. Battery is thereby applied over the a-wire (via U(i)) to initiate seizure of a marker by the succeeding circuit. When a marker is connected to the group selector, low resistance earth is applied to lead a to bring up relay U. Relay J and magnet AM interact, the operate and release time of the former being controlled by the charge and discharge time of condenser Ko66, and the latter stepping the wiper pk in a direction opposite to that of the rotation of the disc so that after a number of steps equal to the first digit it encounters a raised segment and relay Y operates to disconnect the stepping circuit of AM. Relay J sends the digit over wire a in the form of interruptions of potential normally applied thereto. When the succeeding switch is set the low-resistance earth is removed from the wire a and U releases followed by Y. When the succeeding marker is connected up U operates again and the next digit is sent in a similar manner. If the line is an outgoing trunk to an exchange requiring the remaining digits to be sent as earth impulses over the a-wire, battery is reverted over the a-wire to bring up D. Relay is thereby released to enable J to send earth impulses over the a-wire and also to disable the local busy tone source BZ. Metering pulses received over the b wire are repeated by Z to the z wire. If the selector meets all trunks busy condition, battery is reverted on the b-wire to bring up Z to cause busy tone to be reverted. If a called subscriber is found idle then battery is reverted on the a-wire during the release period of Y, to bring up D. When the called subscriber replies, battery is reverted over b. When the caller hangs up A releases, V and EM operate and C releases to bring up K which allows Z to operate battery on the b-wire to revert metering potential over lead z. Relay K brings up U which homes the wiper pk of the storage switch. Release of C causes the eventual release of V which removes forward holding potential on the c-wire. When the subsequent switch train is released, removal of battery on the b-wire releases Z to terminate the metering pulse and D releases followed by K and the circuit is now normal. If the call was to an outgoing trunk F operates to battery received over the outgoing d-wire to revert a corresponding signal over the incoming d-wire. Group selector, Figs. 2a, 2b.-Start relay AN operates to seizing battery on the a-wire followed by E which starts the marker finding switch which is driven by two alternately energized field coils MA, MB. When the group selector is found PA operates to stop the switch by simultaneous energization of both its coils. The connection of battery through the low-resistance winding (i) of PA to the a-wire informs the preceding circuit that digits may be sent. Relay PA operates A, and C follows to release AN and E, the latter disconnecting the field coils MA, MB of the switch. The digit impulses are repeated by PA to A which causes the digit to be registered on a combination of relays H, R, S, T, W. Relay V releases at the end of the train to enable the contact pyramid 1 . . . 0 to mark the first outlet of the wanted group. Relay K then operates followed by G and PA; A and C release the latter bringing up AN, E and D to energize the field coils NA, NB of the group selector. If the " O " level is marked, F comes up signifying a trunk connection. When the marked outlet is reached, relay PA operates, followed by C which puts the stopping of the switch under control of PB. When a free outlet is found, battery on the c-wire operates PB and the switch is stopped. Relay PB releases AN followed by E and brings up PH followed by V which brings up the busy relay CG of the group selector. CG brings up " pressure magnet" AD which presses the speech wipers on to their contacts to complete the speech path. Relays G, PB, PH are released by CG and relay D is released by E. If F is operated, G now reverts battery over the d-wire as a " trunk-busy " signal. Release of D makes the holding of selector busy relay CG the magnet AD dependent on forward earth on the c-wire, de-energizes the field coils NA, NB of the group selector switch and releases A and C, the latter releasing the counting relays and F. Relay V releases K and the marker is now normal. When PA operated it brought up A which adds one to the number registered on the counting chain. In the event of all trunks being busy so that PB fails to operate, PA operates to stop the switch on the first step of the next decade and, with A up, BA now operates and reverts battery over the b-wire as an engaged signal. BA releases G which initiates release of the marker.