Grass Instruments SIU5B Stimulus Isolation Unit and CCU1A Constant Current Unit

GRASS INSTRUMENTS POLYGRAPH DIFFERENTIATOR MODEL 7P20C

VINTAGE Grass Instruments LM4 Lesion Maker / electronics Sci Fi Prop Mid Century

Grass Instruments Polygraph DC Driver Amplifier P511 A.C./ Pre-Amplifier Part S2

Vintage Grass Instruments Model 8A5 (Untested)

GRASS INSTRUMENTS Low-Level DC Pre-Amplifier 7P1-E & F G H L J

GRASS INSTRUMENTS ELECTRODE SELECTOR PANEL RACKMOUNT USED

GRASS Instruments 7P1F Low Level DC Pre Amplifier for Polygraph Lie Detector