Patent GB-387052-A (GB)
Abstract: 387,052. Automatic exchange systems. NICOL, W. E., 149, Broadfield Road, London, and NICOL, F. E., 112, Pickhurst Rise, West Wickham, Kent. Oct. 26, 1931, Nos. 29618 and 33950. [Class 40 (iv).] In a system in which a number of substations are connected over an automatic switching station to a single exchange line, a switch at the exchange is operated correspondingly with a finder switch at the station and gives access to line switches so that individual line switches may be provided for any or all of the substations. Separate meters and other facilities for exclusive lines may thus be provided for each substation. The system described comprises the switching station, Fig. 4, connected by a single line to the switch, Fig. 3, at the exchange which gives access to line switches such as that shown in Fig. 2 for extending outgoing calls. Incoming calls are set up over a final selector, Fig. 1, which is standard except for the provision of a discriminating relay T for holding up the functions of the selector until an extra digit has passed to the automatic switching station. Service may be automatically withdrawn from any substation by an exchange operator. Outgoing calls. The banks and wipers of the station switch shown diagrammatically in Fig. 4 are shown in detail in Fig. 5. The line wires from the substations are connected to the bank of line wiper LW and also to the bank of a commoning wiper CW which is connected to the home contact of LW. The connections for the positive and negative wires are the same except that the negative commoning wiper is grounded. The commoning wipers may be replaced by suitable spring sets. When a substation subscriber closes his loop, S pulls up and connects an impulse lead IM to magnet DM1 of the exchange switch which takes a step and extends the impulse circuit over the positive exchange line to DM2 of the station switch. The switches continue to step over off-normal contacts NB1, NB2 after S falls back and when the calling line is reached, line relay L of the selected line switch, Fig. 2, operates W which opens the driving circuits. During stepping, relay Y busied the exchange line in the banks of the final selector, L now takes over the function and the call is completed in known manner. Incoming calls. The final selector operates in known manner and relay E operated in parallel with rotary magnet R completes a circuit for T. If the wanted line is an exclu. sive one, T falls back when E relapses since its circuit will then include the line relay of the wanted line. If the wanted line is that to the switching station, T pulls up to ground on the negative wire, opens the circuits of the switching relay H and rotary magnet R, and operates relay W, Fig. 3. The next digit is repeated by relay A over the positive wire to a repeating relay or direct to magnet DM1 which on taking a step extends the impulse circuit to DM2 which thereafter is stepped over off-normal contacts NB1, NB2 in unison with DM1, relay Y pulling up during the train to hold T and complete an alternative impulse circuit independent of the positive wiper of the exchange switch, Fig. 3. At the end of the train Y and T fall back, W remains energized in series with switching relay H which operates together with the cut-off relay K in the line switch. The final selector rings the line and completes the connection in known manner. The first Provisional Specification describes a modified final selector in which the digit for selecting the wanted substation is passed over a fourth wiper and bank. Release. Homing circuits for DM1, DM2 from impulse lead IM are completed by the relapse of W, when the subscriber on the automatic switching station hangs up on both outgoing and incoming calls. Withdrawal of service to substation. At the switching station, Fig. 6, subscribers' lines are connected to contacts 1 .. 5 and polarized electromagnets EM are connected to contacts X1 .. X5 so that, by dialling a suitable final digit, an exchange operator may select an electromagnet and by application of current thereto in a suitable direction cause it to disconnect a line. Reversal of operating current reconnects the line.