A new system is described for recording behavioural events on a time scale, in a form which can be fed directly into a computer. The user presses keys on a keyboard to denote behavioural events. The number of separate events which can be distinguished depends on the quality of equipment used, and can be over 60. The main disadvantage of the system is that no two events can be recorded simultaneously. The information is coded on magnetic tape, using an unmodified single channel domestic tape recorder. The encoding unit is light and battery driven, and together with the tape recorder can easily be taken into the field. The tapes are later played back through a simple interface to a small computer. The computer decodes them, and punches out a permanent paper tape record of which behaviours occurred, and when, to the nearest tenth of a second. These paper tapes can then be fed back into the same or another computer for analysis. In addition to recording discrete events, the system can be used as a simple analogue to digital converter. The main advantage of the system is that it is extremely cheap and easy to make. This is because a very simple frequency code is used, and the computer itself is programmed to perform the whole decoding operation.