Patent GB-679447-A (GB)
Title: Improvements in or relating to circuit-arrangements for use in automatic signalling systems
IPC: H04Q3/00
Filed: 1951-02-02
Abstract: 679,447. Automatic exchange systems. PHILIPS ELECTRICAL INDUSTRIES, Ltd. Feb. 2, 1951 [Feb. 7, 1950], No. 2646/51. Class 40 (iv). A wiper-switch is set to a desired outlet by means of a local circuit in which the rotary magnet of the switch is connected to a first test wiper and is energized through this wiper when the switch engages an unwanted outlet whilst a test relay is connected to a second test wiper and is energized at a wanted outlet; if an outlet is reached where neither the rotary magnet nor the test relay is energized, the switch is locked at this outlet which is thereby marked unwanted for other switches and an alarm is given. As shown, a single-motion group selector GK is engaged by applying earth to the c-wire at a preceding stage so that busy relay C is energized by battery Ba. Relay A responds, through its winding A1, to dial impulses and by interchanging earth markings on an " escapement " bank associated with a wiper Td steps the switch to the first outlet of the wanted group, relay B being energized during the impulse train so that rotary magnet D is directly connected to wiper Td. The d-contacts of the " escapement " bank are not multipled to any other switch, whereas the contacts of the other banks shown are multipled to similar contacts of other group selectors. The movement of the switch operates off-normal contacts k. At the end of the impulse train the relapse of relay B starts the switch hunting for an idle outlet in the selected group, rotary magnet D now being connected to a test wiper Te. The e contacts of engaged outlets are earthed through contacts Kv of subsequent switches so that magnet D is energized at these outlets and the switch moves on until an idle outlet is reached where the e-contact is not earthed and magnet D is de-energized to stop the switch. A second test wiper Tc wipes a bank in which each contact is connected to battery Ba through a busy relay C<SP>1</SP> of a subsequent switch. Windings T1, T2 of a test relay T are connected to wiper Tc, and T is energized at an idle outlet. At an engaged outlet the c-contact is connected to earth through a lowresistance winding of a test relay of another group selector and T is not energized. Normally, at an idle outlet, T operates, shunts its high-resistance winding T2, and connects wiper Te to earth, so that the outlet is marked engaged for any other switch. Relay T also switches through the speech conductors to wipers Ta Tb. At the end of the conversation, relay C is released to release T and complete a circuit for magnet D to drive the switch to its normal position where the restoration of off-normal contacts k breaks the circuit. If, due to a fault, an outlet is reached where neither magnet D nor relay T is energized, a relay X operates in series with D which is not energized due to the high resistance of X. Relay X earths wiper Te to mark the faulty outlet engaged, sends busy tone to the caller, lights an alarm lamp LA in a holding circuit for busy relay C, and applies earth to an alarm lead Al. If no outlet in the selected group is either idle or faulty, the switch stops at the last outlet, such as 28, of which the e-contact is never earthed, so that relay X and winding A2 of impulse relay A are energized. The caller receives busy tone, and relay C is released to initiate release of the switch as before.