ScopePar turns a PC into a multi-channel oscilloscope module utilizing the parallel port, the user interface to which is SeriCon on other PC. If you have an old PC, boot it by dos to run ScopePar and control it by SeriCon on your GUI PC through serial port. The free trial version of SeriCon is enough in usual cases. Important features are: a 5 channel square wave oscilloscope. Sampling rates upto around several 100kHz. Trigger modes. Version 1.1 includes system to measure also can be triggered by the output data pins just before a measuremet period starts.