Patent GB-1015311-A (GB)
Title: Telephone systems
IPC: H04Q3/00
Filed: 1963-01-25
Abstract: 1,015,311. Automatic exchange systems. STANDARD TELEPHONES & CABLES Ltd. Jan. 25, 1963 [Jan. 31, 1962], No. 3254/63. Heading H4K. An electronic translator receives a combination of digits to be translated together with progress signals indicative of the digits required; the first digit being caused to enable a transistor to apply current to a plurality of leads each connected via a diode gate to the emitter collector path of a transistor controlled in accordance with the second digit in such a manner that the current is absorbed in all cases except for the transistor associated with the valve of the second digit, whereby a lead corresponding only to the combination of the first two digits is marked; this marking (possibly similarly processed in response to further digits) being used in combination with the progress signal to control the emission of the appropriate translation digit or digits. The arrangement is applicable to a system comprising an information by-path which connects the register to markers associated with the respective switching stages. The translation is located in this by-path and is capable of feeding information both to the markers and back to the register (Figs. 1 and 2, not shown). As shown, Fig. 3, the register feeds the following information as signals or coded combinations of leads:-digit signals over group A, B, C, D; whether the call is national or regional over Fa, Fb; the category (or class) of the calling subscriber over E; and the stage at which the call has reached (and also if an alternative route is to be selected) over G. The digit signals are applied, to decoding arrays dcl . - . dc4 comprising matrices of cross points at appropriate ones of which resistors are cross connected to provide decimal indications on leads fl4 to converting networks AN, AN<SP>1</SP> comprising transistor gates to provide outputs indicative of the desired route. Networks AN or AN<SP>1</SP> are enabled according as the call is national or regional. Assuming the former case, the output from AN is fed via a cross-coupling network RP1 to an amplifier rf associated with the desired route. Amplifier rf feeds the top line of matrix RP2 whose cross connections determine the route category which is fed via cr to the comparator CPR which also receives the calling subscribers category from E and dc5. If the call is permitted gate po1 is opened to admit the signal indicating the stage of this connection in this case first group selection, whereby the first of the gates po2 is opened over lead fl2 to enable the cross connections indicative of the digits (in this case two) required to set the group selector. These are fed to coders co3, co4 whence they are fed out over C<SP>1</SP>, D<SP>1</SP>. At the same time further cross connections feed instructions to the register via co5 and leads YZ instructing the register to repeat the prefix, the " national " signal and the calling subscriber's category when next it demands further digits for second group selection. When the register demands the next translation for the second group selection it sends the same information as before, with the exception that the signal over G causes the second of gates po2 to open to provide the requisite translation (also consisting of two digits). At the same time the register is instructed to repeat the same information as before when demanding the third translation which determines the selection of the outgoing line. This is sent as before (and consists of three digits sent over B<SP>1</SP>, C<SP>1</SP> and D<SP>1</SP>). The fourth translation is similarly sent. This consists of a single digit sent over D<SP>1</SP> and is indicative of the fee. This is subject to modification by gates po3 in accordance with the time of day. Subsequent digits require sending without translation. This is effected by a signal over G which operates gates po4 to cause AN, AN<SP>1</SP> to be by-passed the signals being sent out over leads A<SP>1</SP> ... D<SP>1</SP> (the coders co2 . . . co4 not performing coding functions for signals fed in horizontally). Barred calls.-If the comparator finds that a call cannot be made it opens gate po5 to enable a distributing frame RP4 to feed an amplifier rg associated with an operator or talking machine. This amplifier operates over matrix RP<SP>1</SP>2 to provide the necessary routing digits &c. in a manner similar to rf. If, however, an operator tries to make a barred call the comparator emits a signal over OC which is coded at co5 to transmit a signal over YZ to the register instructing it to revert busy tone. Diversion of calls.-If an all trunks busy signal is reverted from a market associated with one of the selection stages then the register informs the translator over G that an alternative route is required. This signal after decoding is sent to the comparator CPR over fl17. The comparator then operates a gate (not shown) to connect the output of rf via the cross connec-  tion frame RP4 to an amplifier rg, which enables the frame RP<SP>1</SP>2 to provide translations appropriate to the alternative route. The comparator may direct this signal to different amplifiers rg according as the call is from a subscriber or an operator, so that they have access to different alternative routes. If the route category received by the comparator is such as to indicate that no diversion is possible, then the comparator opens po1 as for a normal call. Request for more digits.-The register sends only two digits in first instance and these are normally sufficient to determine the translation. If, however, two digits are not enough the output from AN feeds amplifier rl (indicating that another digit is required (if two more digits are required another similar amplifier, not shown, is energized). Cross connections on frame RP<SP>11</SP>2 then cause coder co5 to send an appropriate signal to the register. The networks AN, AN<SP>1</SP> then deal with the three or four digits received in the same manner as for two digits. Night service.-An output from CM may be fed to AN<SP>1</SP> to modify the routing of certain calls (e.g. to operators) at night. Local calls.-Since these are always authorized no access to the comparator CPR is necessary, and use of amplifiers such as rg and frame RP<SP>1</SP>2 can be used. Cross connecting frames.-Cross connections are made in these frames by removable plugs which may incorporate decoupling diodes. Gating arrangements. Fig. 4.-The digits (A, B) to be translated are received as negative potential on two out of five conductors n01/05, n06/10. In the case of the first group corresponding amplifiers 1a . . . 1e saturate, to earth corresponding wires fl4. These are connected to a decoding matrix dcl having resistances connected at appropriate cross points, the corresponding vertical then moving towards earth. The " national " or " regional " networks are enabled by applying earth as opposed to a normal - ve potential to the horizontals in the resistance crosspoints immediately above the decoding networks dcl, dc<SP>1</SP>l, the verticals being connected to the verticals of the decoding networks. Thus a lead such as fl21 corresponding to the first digit is brought near earth potential to block trl, thereby saturating tr2 to bring wire fl22 to negative potential. The second digit similarly blocks a corresponding transistor amplifier 2N<SP>3</SP> The wire fl22 is connected to ten outgoing wires, one corresponding to each of the values of the second digit. In the case of unmarked second digit wires the potential is shunted to earth by the conducting transistor 2N via diodes such as di<SP>1</SP>2. Only in the case of the marked second digit wire, whose transistor 2N is blocked, can the negative potential exist, so that only the wire appropriate to the combination of the two digits is marked. Similar arrangements using transistors 3N, 4N are used where the code consists of three or more digits.