CCTV SYSTEMS Analog CCTV systems
CCTV SYSTEMS • Analog CCTV systems are still prevalent and in use today, “if it isn't broke don’t fix it” is the prevailing attitude with older systems. • We will look at the many different components that make up these legacy CCTV systems. • As a technician working in the CCTV field it is inevitable that you will come across these types of systems.
CCTV SYSTEMS • Here is a mid 60s CCTV console, notice the rotary phones.
CCTV SYSTEMS • CCTV recording started with the reel to reel system which eventually became smaller and then in the late 70s VCRs (video cassette recorder) were introduced.
CCTV SYSTEMS • Here is a basic analog CCTV system with a 4 channel multiplexer, a time lapse VCR and a monochrome CRT (cathode ray tube) monitor.
CCTV SYSTEMS HERE IS AN OLDER CCTV SYSTEM WITH THE SIGNAL FLOW SHOWN: CAMERAS, MULTIPLEXER, DATE/TIME GENERATOR, VCR, SEQUENCER AND MONITOR.
CCTV SYSTEMS • Current analog CCTV systems have few advantages beyond familiarity and cost. • Analog CCTV relies on time-lapse technology. Storage is limited to low-tech tapes, which make maintenance high and search capabilities low. • Analog has low integration potential and provides no opportunity for remote access.
CCTV SYSTEMS • One of the more commonly known and recognized components of traditional CCTV systems are the cameras. • The first type of camera that was commercially used was a vacuum tube camera, similar to CRT monitors and TVs.
CCTV SYSTEMS • The vacuum tube camera has generally been replaced by smaller solid state devices, but can still be found in some surveillance applications.
CCTV SYSTEMS • Before the mid to late 1980s, a video camera tube or pickup tube was used for converting an optical image into an electrical signal. • Several types were in use from the 1930s to the 1980s. The most commercially successful of these tubes were various types of cathode ray tubes or "CRTs".
CCTV SYSTEMS • Another key component in CCTV systems, especially older ones is the switcher. • A switcher allows the user to select which video source to observe.
CCTV SYSTEMS • switchers are manual or sequencing. • A manual switcher allows the user to select a specific video source by pressing a button on the switch faceplate.
CCTV SYSTEMS • A sequencing switcher changes from one video source to the next at timed intervals. • the time between switching intervals is usually every 5 to 10 seconds.
CCTV SYSTEMS • The camera splitter is a device the allows the transmission of a single signal based on the synchronization of multiple signals.
CCTV SYSTEMS • The splitter allows the user to view multiple camera views on a single screen. • The multiplexer is a replacement for the splitter, it combines the output of multiple cameras into a single composite video signal.
CCTV SYSTEMS • multiplexers are available in increments of four, such as 4, 8, 12 or 16. • the four channel or sixteen channel are the most common. • Having more than 16 images on one screen renders the images unviewable.
CCTV SYSTEMS • A date and time generator is a special type of device that superimposes the date and time onto a video signal. • Date and time generators are through-looped, meaning they do not alter the signal except to overlay date and time data.
CCTV SYSTEMS • The signal is passed on to be displayed on the CCTV monitor.
CCTV SYSTEMS • The date and time generator is less likely to be used in newer installations because date and time functions are often provided by newer DVR systems.
CCTV SYSTEMS • In traditional CCTV systems, video is directed to a VCR (video cassette recorder), it is common to find banks of VCR’s managed by a VCR controller in large CCTV infrastructures.
CCTV SYSTEMS • When using a cassette tape to record, you will generally use a T160 cassette tape for extended recording periods longer than 48 hours or a T120 cassette for shorter recording periods.
CCTV SYSTEMS • Analog systems that utilize VCRs require an operator to change VCR tapes on a daily basis. • These tapes have to be archived for a certain length of time.
CCTV SYSTEMS • VCRs used in CCTV systems utilize time lapse recording to extend the amount of video data that can be stored on a single VHS tape. • Time lapse recording means that each camera has a specific amount of time that is recorded. • The inputs are split across a timing interval and stored on a single recording.
CCTV SYSTEMS • Using the extended recording option eliminates the need to change out cassette tapes often and is useful for an unattended recording session over a weekend or holiday period.
CCTV SYSTEMS • Time lapse recording improves the amount of video data available for offline review.
CCTV SYSTEMS • Film is often projected at 30 frames, meaning 30 images appear on the screen every second. • Since the playback speed and the recording speed are the same, the images onscreen appear to move at normal speed.
CCTV SYSTEMS • Even if the camera is set to record at a slower speed, it will still be projected at 30 frames, thus the image on screen will appear to move faster.
CCTV SYSTEMS • A video cassette recorder (VCR) controller allows the selective control of multiple video recorders. • A typical VCR controller provides several operations to control the actions of a VCR. • Traditional VCR’s provide 7 types of control that are supported by a VCR controller.
CCTV SYSTEMS • The 7 types of controls supported by a VCR controller: • PLAY • STOP • FAST FORWARD • REVERSE • PAUSE • RECORD • EJECT
CCTV SYSTEMS • A VCR controller will often support up to 64 VCR’s, multiple VCR controllers can be connected together in a daisy chain. • This allows control of several hundred recorders. • Alarm function support is also a typical feature of VCR controllers.
CCTV SYSTEMS • A sequencer simply sequences through multiple images and presents them on a monitor at a specified time set by the operator (similar to a switcher). • An operator can sequence through a single image at a time or choose to sequence through four or more images at a time.
CCTV SYSTEMS • The final component of a CCTV system is the monitor, in older systems the monitor has been a black and white CRT monitor.
CCTV SYSTEMS • The typical black and white (mono chrome) monitor in legacy systems is a 19” CRT (cathode ray tube). • 9” monitors are also used but the smaller size is better suited for view of only 1 camera image though with the use of a quad switcher 4 images can be displayed on a 9”. • They’re called monitors because they do not contain any tuners like a normal TV.
CCTV SYSTEMS • Will a regular TV work on a CCTV system? • Will a home VCR work with a CCTV system? Both devices would work however you would need an F to BNC adapter and of course just like the old video games you would have to set your TV and VCR to channel 3 or 4.
CCTV SYSTEMS • Though color TV was prevalent in late 70s and through the 80s, CCTV systems still used black and white monitors. • Black and white monitors have traditionally provided much better resolution than color CRT monitors.
CCTV SYSTEMS • A lot has change with the advent of technology and now the amount of equipment required in legacy CCTV systems has been incorporated into one unit, the DVR (digital video recorder). • In the next lecture we will look at the components that comprise a newer CCTV system, you’ll notice the list of components will be much shorter.