The very first electronic guitar effect I've made was Tremolo, the very first song I've played with it was "Midnight Special", the CCR version, in November of 1969...
This one is the optocoupler-based, phase-shift based design, which means that in addition to amplitude you get some pitch modulation (Magnatone freaks anywhere?). For those who like pure square-wave, high speed amplitude modulation, upgrade is available.
The controls are straight forward - Depth and Speed. Depth takes modulation from zero to 100%, to asymmetrical phase anomalies. LED shows effect On and blinks with corresponding speed. Enclosed in small 110x60x28mm die-cast aluminum box.
Output jack is wired for stereo- use TRS jack and get dry and wet signals separately to two amps or a console.