Apparatus for recording and/or reproducing an information signal

An apparatus for recording and/or reproducing an inforation signal such as a PCM (pulse code modulated) signal and the like is disclosed, in which an index signal (IDX) is inserted (recorded) into a predetermined area portion at a position extended to a recording area of the PCM signal recorded by a rotary head (HA, HB) or the index signal (IDX) recorded is erased therefrom, an area specifying signal which specifies the area of this index signal (IDX) is formed on the basis of an address data (ADRS) in the reproduced PCM signal. According to the apparatus of the invention, the index signal area is always determined at a position having a predetermined positional relation to a recording area (13, 23) of the PCM signal so that when the index signal is inserted into or erased from the index area, the PCM signal portion and other signal can be prevented from being erased.