Signal conversion circuit for interconnecting coaxial cable and a twisted pair

摘要

In typical multi-terminal computer installations, each display terminal is connected to a controller by a coaxial cable (commonly referred to as coax) with a concommitant limitation on the distance from the controller that any terminal can be placed, normally in the range of a few thousand feet. The disclosed invention eliminates the need for a direct coaxial cable connection between the controller and the terminals. In the form of the invention described, two interface units are utilized. The first interface unit is connected to the controller by a single coaxial cable. That interface unit is connected to a second interface unit by a single pair of twisted wire, such as a telephone line. Connected to the second interface unit can be as many as eight coaxial connections to display terminals. Using half duplex operation the controller can then address and poll each of the connected display terminals to transmit and receive data. The distance between the interface circuits can be as great as five thousand feet. If additional distance is required, additional sets of interface units can be used.