Philips DAT850 - Manual (Page 11)

TECHNICAL INFORMATION ABOUT DAT
(Tape Format) ^ I Tape running direction 8.15 mm/sec
Track width 13.591 yum
Tape width 3.81 mm
^------------------------------ ----- 90° with 30 mm dia. head drum (23.501 mm)—^
1
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\ A
. A PCM area
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SUB
ATF area
Sub code area
Direction of head rotation
ATF area
Sub code area
DAT recording system
• In a DAT deck, heads mounted in the head drum rotate at
high speed to record digitally-encoded signals on the tape
at an angle to the tape. This system is called “helical scanning”.
• PCM (music signal) area:
Digitally-encoded music signals are recorded in this area.
• ATF (Automatic Track Finding) area:
This area is used for recording ATF signals which control
the heads so that they trace the recorded signal for accurate
and stable tracking and the correct signals are picked up by
the rotating heads.
• Sub code area:
This area is for recording the signals which enable various
functions such as high-speed search and editing. With the
DAT850, A TIME (absolute time), Program No., Start ID and
End codes can be recorded.
Amplitude
A
Audio (analog) signal > Time
Digital signal processing
• Digital recording in the 48 kHz standard mode
Signals are converted from analog to digital before being
recorded. This is called A/D conversion.
Digital signal JlJnJlJirUlJirir
1. The amplitude of the analog audio signal to be recorded is
detected 48,000 times per second by “slicing” the signal. This
is called “sampling at a frequency of 48 kHz”.
2. The length of each slice is rearranged as 16 data bits. This
is called “16-bit quantization”.
3. Each quantized signal is encoded as a binary number (Os
and 1 s) for digital recording.
• Digital playback
The quantized digital signals recorded on the DAT tape are
reconverted to analog signals through a D/A converter which
performs the reverse operations to those performed in A/D
conversion.
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