[An instantaneous frequency meter used in neurophysiology (author's transl)]

The present communication gives diagrams used for the construction of an instantaneous frequency meter which includes digital counters for measuring the time interval between two action potentials. This interval is then converted into a tension, and the reciprocal is obtained by an analogic process. Instantaneous frequencies measured by this device can be displayed either on an oscilloscope screen or directly on paper through a pen recorder.