Abstract: A position control system for a welder includes a probe pivotably supported on the welding head assembly for motion through an arc extending ahead of the path of motion of the welding head. A sensor supported on the probe connects to a control system which generates an output representing coordinates of points along the center line, and an output proportional to the gap of the line of abutment between a pair of plates to be welded and controls the direction and rate of motion of the welding head along the center line of the abutment as well as the rotation of the head to maintain it in a proper disposition to the seam being welded and to maintain the sensor motion generally in front of the path of motion of the head.

Abstract: A computer system consists of a central station and a plurality of remote terminals, some having a relatively low data acceptance and/or transmission rate and others having a higher data rate. The communication link between the central station of the terminals consists of a low speed channel and a high speed channel. The terminals are permanently connected to receive signals over the low speed channel and a control signal, sent by the central station, to a particular addressed terminal over the low speed channel connects an associated terminal to the high speed channel.