Recording a pulse series on analog tape for fast input into the digital computer.
Much of the data generated by psychological and physiological experiments in general and behavioral experiments in particular are in the fornm of a time series of events. Such data, for example subject responses and single neuron unit activity, are frequently recorded on analog magnetic tape during the experiment and processed later off-line by digital computer. This processing usually occurs at rates conilparable to the original data rates. When the time series of events is presented to the computer from magnetic tape at the original rates, the bulk of the computer processing time is spent waiting for each event. This "idling" time, dedicated to the measurement of the inter-impulse intervals by counting the number of passes of the programl through a timing loop (Krekule, Skvaril, Bures, and Vlach, 1968; Jokinen and Leinonen, 1969) or by counting the number of computer clock pulses (Wyss, 1970) can be reduced considerably by reducing the time scale of the data during the input process. Simply reading the magnetic tape into the computer at a speed many times greater than the recording speed will not result in the precise recovery of the recorded time intervals because these intervals will depend upon tape speed stability, which is reduced at high speeds. However, this dependence upon tapetransport speed stability for the precise recovery of inter-event intervals is eliminated by simultaneously recording, (on the same track as the experimentgenerated pulse series) a series of equally spaced, clock generated, timing pulses. This independence will be ensured even when the fast-rewind mode of the tane transport is used during the reading of the data into the computer. Owing to the higher speed of the tape. the shape of the reproduced pulses may be distorted, so that pulse shape restoration circuitry is require(l This method of recording and reproducing time pulse series is described below. The advantage of the proposed method is in its simplicity. Actually, only the clock-generated timing pulses are recorded on tape. When an experiment generated event occurs during the recording process, the clock pulse next in timne, ordinarily of positive polarity, is reversed in polarity and recorded as a negative-going clock pulse. This is so even when an event occurs simultaneously with a positive-going clock pulse (see Figure 1). The interval between events, therefore, is evaluated during playback by having the positivegoing pulses counted in the computer's accumulator. At each negative-going clock pulse, the content of the accumulator is transferred to the computer's memory, a) -