Abstract: An interface circuit for use in a data transmission system is designed to be used not only between a highway and a device but also to link highways and can be commanded to enter a status in which commands sent to it on one highway are modified and sent out as commands on a second highway so that a controller device on the one highway can control devices not only on that highway but also on the second highway, with extension, if desired, to a third highway or beyond. To achieve this, the interface circuit has two ports each for connection to a respective one of two substantially identical highways, and status control means responsive to signals received at either port to establish different statuses of the interface. For inter-highway communication, the status control means is responsive to a command signal of particular form at either port to produce a modified command signal at the other port.

Abstract: In a multi-device data transmission system with source and acceptor devices linked by a data highway and handshake lines, provision is made for automatically adjusting the delay of the handshake cycle to suit the highway length and other determinative factors. This is achieved in that the acceptors do not accept data until told so to do via one handshake line, whereas the source is only allowed to issue this command when it has been told via another handshake line that all acceptors have seen the data. The system determines its own delay in this way and automatically adapts the delay to whatever length of highway is employed, whether a fraction of a meter in a circuit board or several tens of meters in inter-rack wiring.

Abstract: Digital calculating apparatus, which is particularly suitable for linearizing a digitized output signal produced by a non-linear transducer such as a thermocouple, comprises a store connected in a recirculating loop including combined adder and subtractor circuit, means for changing a number entered in the store to a predetermined target value by a linear or an exponential progression involving groups of N adding or subtracting-cycles, means for counting and storing the numbers of groups of cycles required to achieve the target value, and means for entering another number in the store and subjecting it to the same numbers of groups of M adding or substracting cycles, where M .ltoreq. N, to produce the required answer. For linearizing the digitized output signal x from a thermocouple, where x is given by T = a.sub.o + a.sub.1 x + a.sub.2 x.sup.2 + . . . ta.sub.n x.sup.