The Nagra IV-L is a self-contained high performance sound recorder of exceptional reliability. It will operate in any position. It can be powered either by internal batteries, or an external AC supply using an ATN power unit (not included). It is built to military and aeronautical standards, thus giving the recorder a reliability which has not been available heretofore in the electro-acoustical field. The Nagra IV-L is a single track monaural recorder that replaces the Nagra III PHO synchronous recorder.