Abstract: A method and apparatus for digitally storing episodic signals, such as, electrocardiogram signals is disclosed. In a preferred embodiment, the apparatus includes, for each signal channel, an input amplifier, an analog-to-digital converter, and a double data buffer. The incoming signal on each channel is converted to a multibit digital number a fixed sampling rate. Each multibit digital number is stored in a location in the double data buffer. When a fixed amount of data is stored in the buffer, a processor examines the data to determine the periods during which the signal is undergoing the most rapid rate of change. For these periods, both an indicator of the period, and a first number of data samples per unit time is stored in a bulk solid state memory. Preferably, the data stored is a number relating to the difference between the value of the sample and a number related to the value of the last sample.