Abstract: Position Lock Trigger apparatus employs oscilloscope circuitry and accompanying control software to provide to a user the capability to trigger an oscilloscope on a selected bit position in a received serial bit stream having a fixed pattern length, using either a synthesized, recovered, or external clock source. The selected trigger position can be moved forward and backward along the serial bit stream by one or more serial bit positions at a time in order to examine the entirety of the fixed pattern length serial bit stream, with or without regard to the actual bit sequences occurring in the serial stream.