Abstract: A portable data recorder for recording time-related information on tape cassettes. The recorder includes a briefcase shell in which the other components are mounted, a keyboard having a plurality of keys each of which, when depressed, produces a signal, and a plurality of key lines each coupled to a different one of the keys for carrying the signals produced thereby. A multiplexer, under control of a microprocessor, sequentially samples the key lines and transfers to the microprocessor any signals present on the key lines. The microprocessor then records on a cassette recorder data indicating whether or not a signal was present on each of the key lines sampled, and the time of sampling the key lines. The multiplexer successively samples the plurality of key lines so that both the identity of the keys depressed and the time duration of depression of the keys are recorded.