Patent GB-737778-A (GB)
Title: Arrangement in an automatic telecommunication exchange, for determining to which of a plurality of service classes a desired connection between two subscribers belongs
Inventor: OBERMAN ROELOF MAARTEN MARIE
IPC: H04M15/08
Filed: 1953-10-16
Abstract: 737,778. Automatic exchange systems. STAATSBEDRIJF DER POSTERIJEN TELEGRAFIE EN TELEFONIE. Oct. 16, 1953 [Oct. 21, 1952], No. 28674/53. Class 40 (4). In an automatic exchange, apparatus for determining to which of a plurality of service classes a desired call between two subscribers belongs comprises two groups each of n input terminals, each terminal of each group being connected to each terminal of the other group by means of an individual connection consisting of a pair of resistors in series, a connection from each calling appearance in the exchange switches to one of the first group of n input terminals, a connection from each called appearance in the exchange switches to one of the second group of n input terminals, a first connection from the junction point of the resistors of each of the n<SP>2</SP> pairs of resistors to one pole of a battery, a second connection from each said junction point via decoupling rectifiers to one or more output terminals which are each connected to discriminating switching means, and means for connecting the other pole of the battery via the exchange switch train to the two input terminals associated with the calling appearance of the calling subscriber and the called appearance of the called subscriber, respectively, of a desired call, whereby the discriminating switching means determine the service class to which the desired call belongs. As shown, provision is made for thirty-one classes of calling subscriber and thirty-one classes of called subscriber, each outlet of the line finders OZ and of the final selectors EK being jumpered on a distribution frame to the appropriate one of the first and second groups, respectively, of thirty-one input terminals. The 31<SP>2</SP> junction points of the pairs of resistors R I<SP>1</SP>/ 1 , R II <SP>1</SP>/ 1 , ... , R I <SP>31</SP>/ 31 , R II <SP>31</SP>/ 31  are wired via individual resistors R III <SP>1</SP>/ 1 , ..., R III <SP>31</SP>/ 31  to the negative pole of battery V1, and via individual decoupling rectifiers KC<SP>1</SP>/ 1  ... KC<SP>31</SP>/ 31  to group marking terminals <SP>1</SP>/1 ... <SP>31</SP>/ 31 . With no call being set up, the potential at all the group marking terminals is - V1. However, when the exchange switches have been set in accordance with a desired call, and before switching through takes place, the registercontroller applies ground over the switch train to the two input terminals associated with the two parties to the call. The Specification shows that the potential of the group marking terminal associated with the pair of resistors which has both ends grounded is then less negative than that of any other group marking terminal, and that the amount by which it is less negative increases as n is increased. It is assumed that m different conditions may be applied to the setting up of a call, and that either none, one, or a combination of any number up to m, of these conditions is required to be applied according to the particular one of 2<SP>m</SP> possible service classes to which a desired call belongs. Hence, if an individual two-condition device is provided for each of the m conditions, and each device is operated when the service class requires the corresponding condition is to be applied, the service class is indicated by the combination of devices operated. In the embodiment m is five, and up to 2<SP>5</SP> service classes may be indicated. Each of the group marking terminals is extended via separate rectifiers, such as KC <SP>I</SP>/ 31'  to the relevant ones of five output terminals (I to V), each of which is associated with a trigger pair which will respond to the potential of the group marking terminal associated with the pair of resistors (R I, RII) of which both are grounded, but not to the potentials of other group marking terminals, and in so responding will cause its anode relay PR to change over. Thus the service class of a desired call is indicated by the condition of the five PR relays. To economise in rectifiers, not more than thirty-two group marking terminals which all correspond to the same service class may be connected in parallel to a single group of rectifiers such as KC <SP>I</SP>/ 31  ... KC <SP>V</SP>/ 31 . Calls in certain service classes may be free and those in certain others may be barred. Specification 670,062 is referred to.