Boss RBF-10 Flanger
"The Boss RBF-10 features three basic modulation controls and normal/invert feedback volume, allowing various flanging effects. Also, with the direct sound cut off, this can be set up with a PA mixer to make an effects loop"
While the translation above of the original manual is pretty poor, we can confirm that the RBF-10 is a flanging modulation machine with plenty of different uses.
These use a standard 9vDC Boss power supply (not included).