Data is transmitted via BPSK31 with a phase shift of 180 degrees being a binary 0, and no phase shift being a binary 1. [Craig]’s circuit uses an op-amp and a pair of diodes to do a full wave ...

We’re reminded of those days by [Burkhard Kainka]’s triggered sound generator, which couples an op-amp timer to another op-amp phase shift oscillator to produce a sound described as “the ...