Simultaneous recording of analog signals, audio and video using a VCR

An interface to record analog signals from DC to 20 kHz on the stereo sound channels of video cassette recorders is described. This interface is an effective solution for the implementation of experiments requiring simultaneous recording of electrophysiological analog data, audio and video signals, since all these data are recorded on the same tape. The system requires the construction of a simple analog interface and minor modifications internal to the VCR, required to bypass non-linear elements present on the audio signal path. The particular solution used to adapt for Sony VCR model SLV-575UC is given in full detail. The general requirements the other VCR makes and models must fulfil to make the adaptation feasible and guidelines for the design of interfaces are discussed.