ELECTRONIC CIRCUIT

TTL RS232 driver circuit.
TTL driver circuit consists of 2 transistors and a few other passive components, a negative voltage for RS232 logic generated by the capacitor C7.
TTL to RS232 driver circuit and a variable voltage output driver has a parallel termination impedance to match cable and TTL driver circuit, and provides the best waveform.
When driving [...]

This article is about another method I tried and had 100% success first time. The object is to modify an old plotter pen so that you can draw direct onto the PCB material itself. No photography, just a new pen. All you have to do is the use one of those Faber [...]