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Most areas of video surveillance technology have undergone fundamental changes in the past ten years -- thanks to the growing impact of digital microchips  -- but time-lapse video recording has been stuck in a bit of a time-warp. The VHS cassette system, first marketed 21-years ago this Autumn, still reigns supreme. There’s no shortage of alternative technologies -- both old and new -- but it says something for the format’s robustness, resiliance, performance and economy of use, that it is still around today, and likely to remain with us for a few years yet. 


Panasonic have been a pioneer of the format’s hugely successful role in time-lapse video recording. Since the mid 1980’s they have produced a succession of highly regarded machines. Their latest model is the AG-TL700, a well-featured Super VHS deck, capable of recording for up to 170 hours on a three hour cassette. This gives just over one week’s worth of coverage with a recording interval of 1.12 seconds.


There are eight recording speeds in all, including 3-hour real-time, plus 12, 24, 48, 72, 96 and 120 hours (1/50th, 0.1, 0.18, 0.34, 0.5, 0.66, 0.82 sec intervals). S-VHS recording quality can be very good indeed. Under ideal conditions -- using cameras and monitors fitted with Y/C inputs and outputs -- horizontal resolution can be in the order of 400-lines.  A set of multi-speed playback functions enables recordings to be analysed in detail. Time, date and various other items of information are superimposed on the recording, and the machine has a built-in timer, that can be programmed to switch it on and off at pre-determined intervals, or respond in various ways to alarm triggers.  An hour meter helps the user maintain a regular service schedule and it is compatible with a range of external devices, including a frame switcher.


General design and layout are similar in some respects to previous models, though this machine has a mid-mount deck mechanism, with the display panel beneath the tape loading hatch. There’s a few more exposed front panel controls this time; on the far right are three large buttons, for tape eject, record mode and record-review. The latter operates in the record mode, when pressed the tape is rewound for a few seconds, then it replays, after which it resumes recording. This panel also contains a recessed switch for Summer/Winter time change, and an alarm indicator, that illuminates when an alarm recording is in progress. After it has ended it flashes, to alert the operator.


Six smaller buttons live on the face of the display. They’re concerned with changing the time-lapse mode/ adjusting replay speed, manual tape tracking, display counter reset and counter/alarm search. The remaining controls are hidden behind a hinged flap on the left side of the fascia. They include the main on/off switch, the main replay controls and switches for timer mode and the on-screen display.


Rear panel connections comprise a pair of BNC sockets, for composite video input and output, two mini-DIN connectors for Y/C (S-Video) in and out. There are three phono/RCA sockets, one for a camera switcher output the other two are for the mono soundtrack input and output. Two minijack sockets are used for high-impedance microphone input and external wired remote control. A row of six screw terminals carry connections for the alarm input, alarm reset, tape-end and external alarm sounder.


The machine is configured using a series of menu-driven on-screen displays. Menu 1 covers time and date adjustment, control lock and the hour meter display. Menu 2 has options for positioning the time/date display, a switchable blue background alerts the operator to a loss of video signal, alarm buzzer, tape end, tape remain and error warnings. The third menu screen is used to set alarm responses and recording duration. Recording mode settings can be selected on menu 4, along with various VTR operation routines, such as what happens when a tape is inserted (stop, record or rewind and record), when it reaches the end of a tape (stop, rewind, rewind and record or eject), video signal mode (auto or black and white), input selection (composite or S-VHS), S-VHS recording mode enable, and playback picture quality (outline emphasis, hard/soft detail). The fifth menu is used to set the internal timer, for programming daily or weekly settings. When the machine is in timer standby mode the alarm system remains active and a tape pass counter logs the number of time a cassette has been used in repeat record mode.



The initial settings take only a few minutes to complete, however, we did come across an error in the otherwise easy to follow instructions. This concerned setting the auto repeat/rewind mode, for when the tape runs out. The manual insists this can be done from menu 2 when in fact it is an option on menu 4, which seems somewhat careless. The controls for the on-screen display do take a little getting used to, they’re not especially user-friendly, or logically implemented.


In the 3, 12 and 24 hour modes the tape moves continuously so audio recording is possible; tape motion is intermittent at all other recording speeds, including a second 24 hour mode. Snatches of sound are captured but they’re too short to be of any practical use. If an alarm even occurs when the machine is in a time-lapse mode it automatically switches to 3-hour real-time mode for a pre-set period, or until the tape runs out. At the same time front-panel and on-screen indicators appear and the event is logged and displayed on menu 3. An indicator is also superimposed alongside the time display on the recording, though Panasonic have missed a trick by not  recording an index mark on the tape, which would make alarm recorded sequences easier to find.


The playback controls are not very accessible and it is easy to sail past a particular sequence without meaning too, then waste time trying to find it again. The tape transport controls on Panasonic’s domestic VCR are vastly superior to these, a jog/shuttle control would make it lot easier to study a recording. As it is repeatedly reviewing a section of tape -- searching for an important piece of detail -- can be a very time-consuming, not to say hit-and-miss process.



Super VHS recording quality is superb, our sample managed to resolve 400 lines without any difficulty. Rrdings made on standard VHS tape were hovering around the 250-line mark, close to the performance limits of the system. Noise levels were very low on S-VHS and below average on standard VHS recordings. Colour fidelity is very good, especially when used with Y/C output cameras. The separated chroma and luma components eliminate any cross-colour effects and this is clearly evident  at lower light levels, or when the scene contains a lot of fine detail or patterned objects. Image stability is excellent, more than sufficient for detailed frame by frame analysis. As a matter of interest we discovered the TL700 can also replay NTSC recordings, though the video processing is only partial and the picture is in black and white.


The VHS mono linear soundtrack is fairly hissy at the best of times, recordings made in the 3 and 12-hour modes are not too bad.  Speech is intelligible but there’s a significant attenuation of high and mid-range frequencies in the 24-hour recording mode and it can be  difficult to make out some sounds, especially if there’s a lot of background noise.



The maximum recording time of 170 hours might seem a bit limited, at a time when 480-hour recording modes have become commonplace on mid-range and top-end time-lapse VCRs. However, we suspect that one week’s unattended coverage is adequate for the majority of users. In any event this can be easily extended by using the on-board timer to switch the machine off during low-risk periods. In spite of the slightly awkward transport control layout, the TL700 is refined and generally easy to use. Recording quality is very good indeed, particularly when used in conjunction with a high-performance colour camera (or switcher), with a Y/C output.



Design and design features              ****

Circuitry and components                  *****

Ease of installation and wiring    *****  

Range and variety of functions            ****    

Accompanying instructions                   ****                             

Technical advice and backup            ****     

Value for money                         ****                           




Ó R.Maybury 1997 1808



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