Patent GB-490202-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: 490,202. Automatic exchange systems. PRIOR, U. J. (Mix & Genest Akt.-Ges.) Jan. 4, 1937, No. 17324/38. Divided out of 490,137 under which a Specification was laid open to inspection under Sect. 91 of the Acts, July 5, 1937. [Class 40 (iv)] In a network of the kind 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 arranging that where exchanges represented by the same first two digits are in different zones, but several are in the same zone, a single position of the zone switch is used for these latter exchanges and is connected to an additional bank of the switch registering the third digit. Switch positions may also be reduced as described in Specification 490,137 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 district area 62., exchanges 621, 622, 624 lie in zone IV, exchanges 626, 629 in zone II and all other exchanges 62 . in zone III. For the first three, a single position 3, Fig. 3, is used and the corresponding contact is connected in multiple to the first, second, and fourth contacts of an additinnal wiper (dz<II>) of the switch registering the third digit. For exchanges 626, 629, two separate positions (4, 5) are used, and for the remaining exchanges 62 ., a single late position (20). Since all other exchanges in the main area 6 .. are in zone IV, a further single contact (23) in a still later position will serve for these. Fig. 2 shows the connections to the contacts 1 .. 25 of the zone switch for the network shown in Fig. 1, Fig. 3 shows a circuit arrangement comprising three digit-registers Dx, Dy, Dz and a zone switch z<I> . . z<IV> having its contacts connected in accordance with Fig. 2. Metering is dependent also on the duration of a conversation, two of the digit-registers being used after determination of the zone for recording the duration. Actual metering takes place at the end of conversation under control of an impulse-sending circuit ZG common to a number of conversation circuits. Special provision is made for service calls (first digit 0) which are metered or not according to the value of the second digit. 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. Hunting takes place until relays Px, Py, Pz operate simultaneously. For a call to exchange 583 this occurs in position 1, the relays operating directly over wipers z<I>, dx<I>, z<II>, dy<I>; z<III>, dz<I>, respectively. For a call to any of exchanges 621, 622, 624, the switch stops in position 3, relay Pz(i) operating over wipers z<III>, dz<II>. For calls to exchanges 626, 629, the switch stops in position 4 or 5 and for a call to any other exchange 62, it stops in position 20, the contact in the bank of wiper z<III> being directly grounded since no test is required of the third digit. Similarly, in positions 22 . . 25 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. For a service call Dx and Dy are set by the first two digits, relay Pz(ii) is short-circuited after the first digit (0) so that the register Dz is not set, and relay Q(i) is held energized over wiper dx<I> so that the zone switch does not hunt. When a called subscriber replies, relay M(i) operates energizing relay R which completes restoring circuits for the digit-registers. Relay Q reoperates and switch Dx is stepped every five seconds by a clock contact Ss and after each minute Dy is advanced one step over wiper dx<II>, a warning buzz being given over relay F just before the end of each minute. If the call lasts longer than twelve minutes, relay T operates over wiper dy<I> to break down the connection. When the calling subscriber hangs up, relay F(i) is operated over wire a<1> energizing T which releases R. The grounding of start wire An causes the common impulsetransmitting apparatus ZG to associate itself with the connection over a finder S<I> . . S<III> and relay K operates. Metering impulses are then sent over wire bl, their number being determined jointly by zone-switch wiper z<IV> and time-recording wiper dy<III>. Service connections are metered or not according to the setting of wiper dy<II>, the zone switch being in its normal position.