Magnetic recorder test article and methods

For testing readback circuits of a digital signal magnetic recording system, a sheet-like article having a magnetic signal record portion,

• said record portion having a plurality of substantially parallel elongated signal tracks, each track having a signal with transitions between two magnetic states recorded therein,
• said tracks extending along a first direction and being spaced along a second direction which is transverse to said first direction,
• each said recorded signal having bit cells and ideally a fixed phase relationship to said bit cells,
• the improvement including in combination:
• said phase of said signals varying in a predetermined phase change precession along one of said directions, and
• said signals having a second signal parameter varying in a predetermined change pattern along said second one direction such that combined phase and second parameter relationships exist as a predetermined array in said plurality of tracks.

For testing readback circuits of a digital signal magnetic recorder, a sheet-like article having a magnetic signal record portion,

• said portion having a plurality of substantially parallel elongated signal tracks, each track having a signal with transitions between at least two magnetic states recorded therein,
• said recorded signal having bit cells and ideally a fixed phase relationship to said bit cells,
• the improved article including in combination:
• at least one of said tracks having a test pattern characterized by an initial phase shift, a predetermined number of transitions phase shifted in accordance with said initial phase shift, and additional phase shifted transition having a phase shift substantially different than said initial phase shift whereby digital signal recorders having equalized readback circuits can be phase shift tested.

A test section for an article used to test digital signal magnetic recorders,

• the improvement including in combination:
• a plurality of elongate record tracks each having like recorded signals and each record track having a plurality of test portions for facilitating measurement of head-to-medium spacing, said test portions aligned transversely to said tracks,
• first and second full signal amplitude portions bracketing along the track length of each said test portions, and
• said test portions extending having differing energy contents for inducing errors during readback at a given energy content for a given head-to-medium spacing in accordance with track location of said given energy content test portion on said article.

The method of testing a signal processing circuit,

• the steps of:
• supplying a signal to said circuit,
• supplying an initial phase trigger phase shift as a part of said signal to perturb said signal processing circuit, and
• supplying a second phase disturbance in said signal a predetermined time after said initial phase trigger for testing recovery of said signal processing circuit from said initial phase trigger.