Oscilloscopic recording of muscle fiber action potentials. The window trigger and the delay unit

Abstract

This paper deals with some technical problems in connection with the oscilloscopic recording of single muscle fiber action potentials. The action potentials trigger the sweep of the oscilloscope to permit a fast time base and comparison of the shapes of consecutive action potentials. By means of the delay unit it is possible to record on the oscilloscope the part of the action potential appearing up to 500 μsec before the triggering point. With this unit it is also possible to trigger the oscilloscope sweep on the fast positive-negative deflection of the action potential, thereby obtaining a much steadier display than when triggering on the initial positive phase. By means of the window trigger it is possible to record action potentials of any given size. Only action potentials having a positive peak lying within two fixed limits (which can be selected) will trigger the oscilloscope. The counter gate, which allows automatic time interval measurements only of those action potentials that are displayed on the oscilloscope, is finally described. The electronic design of the window trigger. The construction is based on Philips' circuit blocks (two No. B8 950 00 and two No. B8 950 01).