Optoelectronic tremolo, like an old Fenderamp tremolo. Adjustable in speed and depth . The frequency of the LFO is check by a yellow led.

Technical details:

Inputimpedance: >500KOhm
Outputimpedance:100KOhm
Gain: max. approx. +/- 0dB In- and output: 1/4" Jacks
Controls: Spee, Level
Switch: 3PDT-Switch Effect On/Off
Jack for extended power supply: 9V
DC/2,1mm
LED indicator for effect ON (red), Speed (yellow)
Power supply: 9Volt /6F22
Power consumption: approx. 3/6mA
Measurement: (LxWxH) 110x60x30mm)
Weight: approx. 280g without battery