Apparatus and methods for audio tape indexing with data signals recorded in the guard band

A method for providing indexed audio on a magnetic tape, said magnetic tape comprising a right channel track and a left channel track for recording and reproducing stereo audio signals, comprising the steps of:

• shifting the frequency of data to frequencies higher than the bandwidth of the audio signals;
• recording the frequency shifted data in a guard band interposed between and parallel to said right and left channel tracks;
• recording a plurality of programs onto the left and right channel tracks with spaces on the channel tracks between the programs;
• and
• recording a non-audible program presence signal onto the left and right channel tracks coincident with the plurality of programs wherein the nonaudible program presence signal is not recorded in the spaces between the programs.

A method for providing indexed audio on a magnetic tape, said magnetic tape comprising a right channel track and a left channel track for recording and reproducing stereo audio signals, comprising the steps of:

• determining whether the tape is an indexed tape;
• searching the tape to find an area of the tape with no program presence signal, wherein the program presence signal indicates the presence of a program coincident with the program presence signal;
• rewinding the tape to a beginning of the area with no program presence signal;
• and
• playing the tape at play speed to read directory data from a guard band interposed between and parallel to said right and left channel tracks.

An apparatus for audio tape indexing comprising:

• two signal tracks on an audio tape used to record a plurality of segments, each segment comprising a program and a directory, the directory in each segment comprising data for accessing other programs recorded on the tape;
• means for recording a nonaudible program presence signal onto the audio tape, the nonaudible program presence signal being only recorded coincident with the programs recorded on the tape;
• means for detecting a portion of tape having an absence of the nonaudible program presence signal;
• means for rewinding to a start of the detected portion of tape having the absence of the nonaudible program presence signal;
• and
• means for reading the directory in the portion of tape having the absence of the nonaudible program presence signal.

A method for audio tape indexing comprising the steps of:

• recording a plurality of segments on two signal tracks on an audio tape, each segment comprising a program and a directory, the directory in each segment comprising data for accessing other programs recorded on the tape;
• recording a nonaudible program presence signal onto the audio tape, the nonaudible program presence signal being only recorded coincident with the programs recorded on the tape;
• detecting a portion of tape having an absence of the nonaudible program presence signal;
• rewinding to a start of the detected portion of tape having the absence of the nonaudible program presence signal;
• and
• reading the directory in the portion of tape having the absence of the nonaudible program presence signal.