GB1208329A - Device for selective call sending - Google Patents

Abstract

1,208,329. Automatic exchange systems. INTERNATIONAL STANDARD ELECTRIC CORP. 23 May, 1968 [30 May, 1967], No. 24691/68. Heading H4K. In a register-sender (e.g. for an operator's keyset) in which directory numbers stored in the register are forwarded as combinations of frequencies selected by a matrix, repeated sending in the event of a group of consecutive identical digits is avoided by sending a special frequency signal for the second, fourth, sixth &c. digits in that group. The arrangement described is incorporated in a device for selectively calling mobile radio receiver stations. One frequency per digit is used with an eleventh frequency used as a repeat signal. The matrix has eleven parallel input conductors, each connectible to a corresponding oscillator supplying the corresponding frequency, and five output conductors orthogonal to the first set and corresponding one to each digit to be sent. The keyset has ten digit keys, each of which when depressed closes two contact pairs. The first pair of contacts of each key are coupled in parallel and advance a sequencing arrangement for each digit entered, while the second pair of contacts of a key connects in series two out of five relays in the register and allotted by the sequencing circuit to store that digit. The two relays thus enabled by a digit each close a set of contacts. The input and output conductors of the matrix are coupled at the cross-points by series combinations of two contact pairs associated with different relays of the set of five relays storing a digit so that only one path is completed, connecting one of the ten digit representing frequencies to one of the output conductors. Each pair of adjacent output conductors is tested by a comparator relay which is enabled by a closed loop path through correisponding cross-points associated with the two output conductors if the corresponding digits are identical and the path has not been interrupted by a contact of the comparator relay associated with the first output conductor of each pair and the previous output conductor. Those comparator relays which are enabled, block the transmission of the digit value indicating frequency on that output conductor and gate the eleventh or repeat frequency into that output. When the digits have been transmitted the apparatus is adapted to send a twelfth spacing frequency and to recycle once to again send the wanted number.