Sony DSRPD170 Operating Instructions Manual page 92

Setting time values
Drop-frame mode
In the NTSC standard, the time code value is based on 30 frames per second, but the
exact video frame frequency is in fact 29.97 frames per second and the real time, or 18
frames per 10 minutes.
Drop-frame mode corrects for this by skipping two frame counts at the beginning of
every minute which is not a multiple of ten.
In non-drop-frame mode, however, no frame counts are omitted, and there is a gradual
deviation of the time code from real time.
Making the time code continuous at back space editing
Set TC MAKE to REGEN in the menu settings to make the time code continuous when
the recording has been interrupted or when the cassette tape has been removed from
the camcorder between shootings.
When the camcorder is in recording pause mode, the recorded time code is read from
the tape and synchronized to the internal time code generator.
Once you set TC MAKE to REGEN in the menu settings
Even if TC RUN is set to FREE RUN in the menu settings, the running mode is
automatically set to REC RUN.
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