Pelco Manual C650M (12/98) 9
2.0 OVERVIEW2.1 INTRODUCTION TO TIME-LAPSE RECORDERS
Time-lapse recording permits longer than ordinary recording times. The primary
reason for using time-lapse recording in a CCTV security system is that a single
VCR tape can be used for an extended period of time beyond the standard record-
ing time. The following explains how time-lapse recording works.
The actual recording on VCRs is a series of still pictures or fields. Standard con-
sumer VHS recorders store 60 fields (30 frames) per second. A T-120 cassette lasts
just two hours in this mode (SP mode). You can get slightly longer recording times
(six hours) using the extended recording mode (EP mode). You can record even
longer on a T-160 cassette in these modes: two hours and 40 minutes in SP mode
and eight hours in EP mode. (Refer to the table in Section 8.1.1 for actual recording
times in different modes.)
Time-lapse VCRs, however, use microprocessor-based techniques to record fewer
fields per second than a normal VHS machine and extend recording time. This ne-
gates the need to change the tape every two hours–and also substantially reduces
viewing time when the recording is played back, another important consideration.
In normal VCR operation, all video head scans (60 per second) are recorded. But in
time-lapse mode the tape runs more slowly and records pictures periodically. In 12-
hour mode, a normal time-lapse machine records 10 fields per second, and in 24-
hour mode, it stores just five fields per second (for up to 12 and 24 hours on a tape,
respectively). Longer times are possible by slowing the recording rate further.
At normal speed a picture is recorded every 1/60 of a second so there is little change
over five frames. In longer time-lapse modes, however, a field is recorded intermit-
tently over a longer period of time so changes are apparent from field to field.
The time-lapse recording can be played back at normal two-hour tape speed, which
makes for rapid review–one of the time-lapse recorder’s most important advan-
tages. Action on the tape, however, appears faster than normal.
As an advanced feature, time-lapse recorders (like the TLR2024) can automatically
switch from time-lapse to real-time recording when an alarm condition occurs. This
is important since the primary purpose of recording an event is identification, and
real-time recording provides more detail.
2.2 TLR2024 FEATURES AND FUNCTIONS
The TLR2024 time-lapse VCR is a powerful surveillance tool designed for industrial
and security recording. In addition to ordinary two-hour and six-hour recording modes,
it has time-lapse modes that allow recording in 12- and 24-hour modes. The TLR2024
features frame-by-frame playback and high-speed playback of longer recordings.
Audio Recording–Audio recorded in 2H, 6H, L(inear)12H, or L24H modes is played
back only in its respective mode.
Resolution And Image Quality–This VCR has a high-quality circuit allowing more
than 330 lines in B/W (black and white) mode, and more than 240 lines in color
mode.
Automatic Head Cleaning–The VCR automatically removes foreign matter from
the heads when a cassette is inserted for continuous smooth operation.
Easy Setup Using A Monitor–The on-screen menus simplify setup programming.
You can select these menus even without inputting a video signal.
Easy Cueing With Alarm Recording–Index signals are automatically added at
the beginning of alarm recording for easy cueing. You can even use the monitor to
confirm the starting time of alarm recording.