Patent GB-490137-A (GB)
Title: Circuit arrangement for the metering of different grades of connection in automatic telephone systems
IPC: H04M15/10
Filed: 1937-01-04
Abstract: 490,137. Automatic exchange systems. MIX & GENEST AKT.-GES. Jan. 4, 1937, No. 204. Convention date, Jan. 3, 1936. [Class 40 (iv)] In a network of the type shown in Fig. 1, comprising main exchange areas having characteristic digits 5 .., 6 .., &c., district exchange areas 58., 62., &c., and sub-exchanges 584, 621, &c., in which the zone I .. IV of a call from an exchange A (584) is determined by a switch which hunts for a position marked in accordance with the three exchange digits dialled, the number of switch positions is reduced by allotting a single contact in the later part of the bank to exchanges which have different second or third digits, but all lie in the same zone. For example, in the area 58, exchanges 583, 584 lie in zones II, I, respectively, and these are allotted to separate positions (1 and 2) of the zone switch, but all other exchanges 58 .. lie in zone III and a single contact (16) may be employed for all these. Similarly, since all other exchanges 5 .. are in zone IV a further single contact (21) in a still later position will serve for these. Fig. 2 shows the connections to the contacts 1 .. 24 of the zone switch for the network shown in Fig. 1. Positions 10 .. 15 are reserved for new exchanges, e.g. 587 (zone II) requiring separate positions, and positions 19 and 20 for extensions of the group 58 .. 62. Fig. 3 shows a circuit arrangement including three digit-registers Dx Dy, Dz, and a zone switch z<I> .. z<IV> having its contacts connected in accordance with Fig. 2. Circuit operation, Fig. 3. Relay Q is normally energized over relay Pz(i) and wiper z<III> in position O. When the circuit is seized, relay C operates over wire c<I> and energizes relays Px (over wipers z<I>, dx<I>), Py (over wipers z<II>, dy<I>), and Pz(ii) (over wiper dz<I>). The impulses of the three exchange digits are repeated by relay A to magnets Dx, Dy, Dz, in turn, relays Px, Py being released at the end of the first and second digits, respectively, under the control of relay V. At the end of the third digit, relays Pz, Q, release and magnet Z of the zone switch is connected to interrupter RU. For a call to exchange 583, relays Px, Py, Pz all operate in position 1 to stop the zone switch which by wiper z<IV> determines that the call is to zone II. Similarly for a call to the home exchange 584, the switch stops in position 2. For calls to all other exchanges 58., the switch stops in position 16, the contact in the bank of wiper z<III> being grounded independently of wiper dz<I> since no test is required of the third digit. Similarly in positions 21 .. 24 no test is required of either the second or third digit and contacts in the banks of wipers z<II>, z<III> are directly grounded. If a non-existent exchange combination is dialled, the switch stops in position 25. At the end of conversation, relay M operates, connecting wire a<I> to relay F to start a switch which transmits metering impulses at contact u1 until contacts tr are opened by a relay operated over one of the zone bars I .. IV and wiper z<IV>. The Specification as open to inspection under Sect. 91 comprises also a similar but modified system. This subject-matter does not appear in the Specification as accepted but forms the subject-matter of Specification 490,202.