EVALUATION OF THE NUMBER OF DEVICES IN A GIVEN CONDITION

摘要

1319835 Automatic exchange systems TELEFONAKTIEBOLAGET L M ERICSSON 21 Aug 1970 40507/70 Heading H4K An arrangement for determining the number of devices active on an evaluating occasion, incorporates an arrangement of circuit components selectively switched into circuit in accordance with the number of devices that are active to provide an impedance value characteristic of said number, and a comparison device bridge or differential amplifier) and employs a succession of evaluating steps each reducing the possible range in which the value lies until said number is uniquely identified. The arrangement described is used for traffic metering within a telecommunications system. As described a plurality of similar systems are controlled by a common timing signal supply 7. Each system includes a stepping switch 2 which steps to successively connect to groups conductors a, b and c to devices 3. Each device is associated with an identical resistance such as Rn which when the device is in use is connected to its groups conductor. Each group includes say 31 devices. For each step of the switch 2 the number of active devices, i.e. the number of resistors R 1 to Rn within a group which are connected in parallel by closure of their associated contacts is determined. To effect this a reference resistance equal to that of about 16 of the resistors R 1 to Rn in parallel is compared in a bridge or differential amplifier with the actual resistance offered by the number to be determined. The result of the comparison indicates whether the number of active devices is 16 or more or less than 16. If, for example, it is 16 or more, a second reference resistance corresponding to about 8 resistors R 1 to Rn in parallel is switched in parallel with the first reference resistance to determine whether more than 24 devices are active. Using further reference resistors corresponding to about 4, 2 and 1 resistors R 1 to Rn in parallel in successive comparisons the exact number of active devices can be determined. At each step the number of active devices and the time are punched out on a tape 6. A relay selection circuit for the reference resistors for connection to a differential amplifier arrangement is described.