The schematics describes a circuit to use a composite video monitor on a PET computer. It is a part from Nick Hampshire's "PET REVEALED". This info comes completely without warranty! Here is the text that accompanies the schematics: ----------------------------------------------------------- Although primarily intended for use by the diagnostics the top connections of the user port can be used for other purposes. One of the most useful, with particular application in schools, is the ability to use three of these lines to drive an external large screen TV monitor. These three lines provide the user with the vertical sync signal on output 9, the horizontal drive on 10 and the video output on line 2. To drive a standard TV monitor (not a domestic TV set) these signals must be combined to give a single composite video output which can be connected directly to the monitor input. The circuit to do this is shown in Figure 2 it will rewuire a 5 Volt power supply which can come from a battery or from pin 2 on the 2nd cassette connector. You may encounter problems with the horizontal hold but this can usually be cured by adjusting the value of R1. Other problems may occur as a result of using very cheap monitors or converted TV sets. If you intend to build this circuit then the actual layout of the components is not critical and it is most easily constructed on a piece of Veroboard. -----------------------------------------------------------