A Holter-type recorder unit for use with an ambulatory ECG recording system is described. The recorder features real-time beat differentiation, including ST analysis and paced beat analysis of two or three channel sampled electrocardiogram data. The recorder also features real-time coding of beat morphology and summary information on cassette tape. Further, summary information for an entire analysis can be compiled and reverse recorded onto the cassette tape at the end of the analysis to allow downloading thereof into an ECG scanner while the cassette is being rewound.