GB1051132A - Improvements in or relating to telemetering systems - Google Patents

Abstract

1,051,132. Electric selective signalling. SHAND & JURS CO. May 23, 1963, No. 20646/63. Heading G4H. A central station in a telemetering system is normally in communication with alarm units via at least one field station, but the latter can change the communication to a control or data transducer when the transducer is selected by the central station. In the normal mode, a counter at the central station addresses the field stations in turn by sending for each a five-bit (binary) primary address followed by five ONES (to indicate that this is the normal mode)-sync. and end-ofcharacter bits are also provided. On recognizing its address, a field station returns the address to the central station for checking and scans two-state apparatus units connected to itself in turn (Fig. 10, not shown). Those units in a first state set corresponding flip-flops which cause associated permanent lash-ups of diodes to be scanned to provide the addresses of the units in 2-out-of-5-code, which are sent to the central station. The diodes associated with units not in the first state are skipped without delay. At the central station, if the returned primary address was valid and if the unit addresses are verified to have two ONE bits, lamps corresponding to the unit addresses are lit and punch-out occurs. Timing at central and field stations is started by sync. bits received each character time but if the expected signal from a field station does not arrive after a certain delay timing is restarted at the central station anyway. A control or data transducer can be selected by specifying its (binary) primary and secondary addresses, the former specifying the field station and the latter its location with respect to the field station. These addresses are transmitted, and returned for checking. If the check is good, a lamp corresponding to the address is lit at the central station, and data may be received from the field station or control signals transmitted thereto. If the selected transducer is a data transducer, data characters in 2-outof-5 coded form are sent from the field station, checked and displayed on character-shaped arrays of lights if correct. A character is also sent to indicate the type of data and all (correct) characters are punched out. A control or data mode cycle is followed by a normal cycle starting at the same field station, the address being forced into the addressing counter. End of message characters are used in transmissions, and when the central station receives one it retransmits it to all field stations. Application to the petroleum, chemical and electric power industries is envisaged.