Home Defence Security

31/10/2014

17/09/2014

21/08/2014

Who trusts Italian engineering?

13/08/2014

13/08/2014

CIF, QCIF, 2CIF, 4CIF. Sounds like a bad nursery rhyme, right? If your eyes glaze over when you hear terms like these you are not alone. In this FAQ, we will attempt to demystify the terminology and put it into a framework that's easy to understand and use.
The table below lists some of the more commonly used resolution terms in CCTV applications. Any resolution over 1 million pixels is considered 'megapixel'. In the case of megapixel cameras, the labels are approximate. For example, a 2 megapixel camera actually captures 1,920,000 pixels per frame. A 3 megapixel camera captures 3,145,728 pixels per frame.
Term Pixels (W x H) Notes
QCIF 176 x 120 Quarter CIF (half the height and width as CIF)
CIF 352 x 240
2CIF 704 x 240 2 times CIF width
4CIF 704 x 480 2 times CIF width and 2 times CIF height
D1 720 x 480 aka "Full D1"
720p HD 1280 x 720 720p High Definition
aka "HD-SDI"
960p HD 1280 x 960 960p High Definition
a Sony specific HD standard
1.3 MP 1280 x 1024 aka "1 Megapixel" or "1MP"
2 MP 1600 x 1200 2 Megapixel
1080p HD 1920 x 1080 1080p High Definition
3 MP 2048 x 1536 3 Megapixel
5 MP 2592 x 1944 5 Megapixel
Table 1. CCTV Resolution Standards (from low to high resolution)
These terms may be used to describe the size of the image captured at the camera, transmitted over a wire, displayed on the screen, or recorded on the hard drive.
When comparing megapixel camera specifications you may notice pixel counts slightly different from the above. This is because some cameras will specify the total number of pixels captured by the sensor, and others will specify the 'effective' pixels. Some of the total pixels are used to contain technical housekeeping type of data, and are not contributing towards the 'effective' details of the image.
Those of you familiar with CCTV know that the resolution of an analog camera is typically listed as "TV lines". These "lines" refer to the horizontal resolution of the image; therefore a 700 line camera has better resolution than a 420 line camera. Digital video recorders, however, list their resolution according to the terms in the chart above. DVRs that are 'Full D1' can record all the detail captured by the highest resolution analog cameras.
One of the most common questions we get is "What resolution camera should I buy?" Of course, it depends. Each camera in your application may require a different resolution. It comes down to how much detail you want, what platform (if any) you already have in place, and how much is your budget. Examples of applications where you can easily justify spending more for higher resolution are recording monetary transactions, desiring facial recognition, or reading license plates.
It is important to consider what platform your camera will be running on as that may limit your resolution options. To summarize CCTV platforms: Analog cameras transmit over coax and can capture up to 700 lines (approximately full D1). HD-SDI cameras capture higher resolution images then encode / decode the data to run over coax. IP or network cameras transmit over CAT5 (just like computers). You can run analog cameras on a CAT5 network, or IP megapixel cameras over coax, but it would require additional hardware and added complexity so it's not recommended.
We do not often recommend HD-SDI cameras because there are shortcomings with the current technology (a topic for another discussion). High resolution megapixel cameras are fantastic and are becoming more affordable. But don't expect results like you see in the "CSI" TV shows - that's just fiction. And keep in mind that the higher the resolution of the cameras, the more bandwidth and hard drive space you will need to transfer and store it. In most cases, cameras over 2MP are usually not worth the extra cost (at today's prices), especially considering the added costs in required bandwidth and hard drive storage.
It's useful to know that the human eye is more sensitive to horizontal resolution than vertical resolution. So for example, to the human eye, there is not much perceived difference between 2CIF and 4CIF. The other issue to know about the human eye has to do with frame rate. The human eye can perceive about 15 separate visual images per second (frame rate). So any frame rate higher than 15 frames per second (fps) is perceived as smooth motion. In CCTV the maximum frame rate available per device is typically 30fps and that is considered 'real time'. But anything over 15 fps is going to look pretty good. Some devices will list different resolutions at different frame rates. So for example, an IP camera might document its resolution as "3MP at 20fps" or "2MP at 30fps". We would recommend using the "3MP at 20fps" setting in this case.
In a CCTV application you will have many cameras with different resolutions but usually only one recording device. So make sure that the recording equipment you choose has at least the resolution capability of your highest resolution camera. Also, make sure it has enough hard drive space to record all of your cameras for a reasonable period of time given your application. Image resolution is most crucial when something happens and you need to playback that video. If you need to zoom in on a piece of video, the quality of that zoomed in image depends on the recorded resolution. So configure each channel of the DVR separately to record at the highest resolution that matches the camera.

One question you may ask yourself is whether the smaller resolution standards are even worth mentioning given today's megapixel capabilities. But QCIF and CIF are still relevant when considering mobile devices. Images on a phone are usually displayed at QCIF for example. Just to be clear, the image may be captured and stored at megapixel resolution but transmitted by the recorder and displayed at QCIF on the mobile device.

13/08/2014

09/07/2014

How to Choose the Right Gate Automation
The number of home-owners who are looking at the benefits of adding automated electric gates to control access to their property is increasing. But, as with all things where you call in an expert to specify and install the equipment, how do you know what's right for your situation and preferences? To answer a lot of questions regularly asked by home-owners concerning gate automation, here's a run-down of the different systems available and why one is better than another in certain circumstances.
Sliding automatic gates vs automatic swing gates
Most people think of gates that swing open and closed on hinges mounted on gate pillars when they consider gates for their driveways. But a pair of automatic gates that swing open and closed require a lot of empty space to clear their full range of travel. Electric gates with a span of 3 metres each still need 3 metres of space behind the gate pillar to swing into when they open. And, unless they have a large space under them when closed, they can't swing onto a rising driveway or they will hit the ground at the bottom as they open.
Another issue with swing gates is the potential installation on driveways where cars are parked just inside the gates. If the home-owners can't get their cars into and back out of the available space with gates open, or the gates can't close once cars are parked, swing gates are not possible.
The solution could be a sliding gate or (less common) pair of gates. These slide along a track installed in the driveway across the entrance width which extends for the length of the gate beyond the opening. The gate slides along this track revealing the open gate-way. In many cases, this will slide alongside an existing fence, hedge or wall next to the gateway as along as this does not curve towards the property within the length of space the gate would travel into as it opened.
Other factors that might determine the type of gate chosen could include weight as a very large, heavy gate is more likely to be a sliding gate than a swing gate. This is simply because of the equipment and forces required to support and open and close a swing gate compared to those required to push or pull a sliding gate along a track.
What sort of gate motors open and close automated gates?
All sliding gates are automated by a gate motor of the same type. This is essentially a motor housed in a box that rotates a cog that protrudes from the side of the box. The motor housing is mounted against the gate so that the cog meshes with a toothed rack that runs the length of the gate near its base. As the cog turns, it pulls and pushes the gate open or closed along it track.
Most swing gate motors have a difficult job as they are mounted on the gate posts or pillars and force gates open and closed from a point on the gates quite close to the pivot point. Imagine pushing a door closed from close to the handle as far as possible from the hinges and force required is low. Now move closer to the hinges and try pushing the door shut and you'll need much more force to do so. This is the effect produced by leverage and simply means that you can move a lever (gate in this instance) much more easily further from the pivot (hinges in this case).
Gate motors used for automating swing gates come in a variety of styles as follows:
• Articulated arm gate motors
• Ram gate motors
• Underground gate motors
Gate motor designers and engineers have come up with a variety of ways of dealing with this problem as can be seen by the number of different types of gate motors available compared to just the one type for automating sliding gates.
All gate motors are essentially electric motors or pneumatic actuators rotating an output shaft.
Articulated arm gate motors
In the case of articulated arm gate motors, the output shaft emerges vertically from the base of the gate moor housing and is fitted to a jointed metal arm mounted perpendicularly to the shaft. The other end is of the arm is mounted on the gate and as the motor turns, it pulls the arm away from the gate which follows it and consequently opens. The reverse happens to close the gate.
Underground gate motors
Underground gate motors work in a similar way but are mounted below the surface of the drive at the base of the gate piers, pillars or posts and the output shaft emerges vertically from the top of the housing in the same vertical plane as the gate hinges. An arm on the output shaft is bolted to the bottom edge of the gate and the gate opens as closed as the output shaft turns. This type of motor requires a lot of force to open and close gates as it is a close as it can be to the gate hinges. However, this type of gate motor should be favoured in South Africa as it’s unobtrusive, near invisible design is very useful
Ram gate motors
Ram gate motors operate automatic gates by pushing and pulling a ram mounted to the gate. The body of the gate motor is mounted to the relevant gate post and as the ram is pulled into the motor housing, the gate opens and as it is pushed back out, it closes the gate.
A similar gate motor to the ram has the gate mounting on a worm screw which rotates and screws the gate mounting away from or towards the motor mounted on the gate post. This again, either pulls the gate open or pushes it closed.
What gate motors work best where?
Articulated arm gate motors
Articulated arm gate motors need room for the arm to move into so are not suitable for gate that open onto walls or where there are restrictions behind the post. However, they are great for installing on wider pillars and where the geometry would be difficult to get spot on.
Underground gate motors
These gate motors are perfect for automating gates as discretely as possible.
Ram gate motors
Ram gate motors are slim and unobtrusive. They are suited to slimmer pillars but require care when aligning the motor and the gate.
Worm screw gate motors
Worm screw gate motors are often slim and don't show any moving parts unless looked at from above or below. They are suited to slimmer pillars but require care when aligning the motor and the gate.
Wheeled gate motors
These gate motors work particularly well on uneven or sloping drives as they can include spring loaded wheels that follow contours as they turn. They also operate as far from the hinge as possible so are used on large swing gates.
24Vdc or 230Vac?
Historically, mains Voltage motors ran hot when the duty cycle was high and so they were used to power hydraulic systems and were cooled by the hydraulic oil. As the market grew, competitors with no hydraulic equipment used low Voltage systems to automate gates as these did not experience the same overheating issues. Today, most systems use either mains (230Vac) or low Voltage (24Vdc) electromechanical systems although some still use hydraulic gate motors.
Low Voltage systems come with obstacle detection as standard which either stops the gates or stops or reverses the gates when they encounter an obstacle during operation. Mains gate motors traditionally did not have this feature but it is being incorporated more.
Low Voltage systems also offer the advantage of battery back-up as they can be operated by rechargeable batteries in the event of a power failure. The downside to Low Voltage gate automation systems is a slightly higher price initially.

09/07/2014

09/07/2014

Centurion D5 Evo Motor kit on special just till the end of August .00 incl Vat supplied only
Hurry and get your while stock lasts

07/07/2014

How Alarm Systems Work

Electronic alarm systems are made up of three component parts designed to detect, determine and deter criminal activity or other threatening situations. An alarm system can detect an event such as an invasion, fire, gas leak or environmental changes; determine if the event poses a threat; and then send a notification about the event.

Detect

The component of an alarm system that detects activity is called a sensor. Here are some common types of sensors that may be used to protect your home.

•Door and window contacts are switches that indicate the opening or closing of a door or window. The switch is mounted to a door or window and is held closed by a magnet attached to the frame. When the door or window moves away from the magnet, the switch opens and it is sensed by the alarm control panel.
•Motion Sensors can detect movement or motion in a large room.
•Glass Break Detectors are designed to constantly listen for the sound of breaking glass. When the glass break detector hears the sound pattern caused by shattering glass, it sends an electronic signal to the alarm control panel.
•Shock Sensors can detect an intruder that is using force to pound through a wall, roof or other area of the structure.


•Carbon Monoxide (CO) detectors are used to detect carbon monoxide; an invisible, odorless, colorless gas. Upon detection of CO, the sensor will send a signal to the control panel, which will then emit an audible alarm.
•Panic Buttons send an immediate, discreet call for help upon the press of a button.
•Environmental Sensors react to the presence of water or sudden increases or decreases in room temperature.
•Smoke Detectors are designed to detect fire. There are two types of detectors: ionization and photoelectric. The most common smoke detector, ionization, is best used to detect flaming fires without a lot of smoke. Photoelectric detection reacts to smoldering fires that produce large amounts of smoke. Both technologies are required to perform at the same level in a fire and provide the same amount of warning. The most effective smoke detector is one that combines both forms of detection.

•A Keypad is a device that is used to arm and disarm an alarm system. Keypads are generally installed near the entrance or exit of home. If a door or window is opened when the system is activated, the keypad will immediately initiate an alarm.

Determine

The alarm system control panel is the brain of the system. It carries out the decide function by processing the information it receives from various sensors and responding accordingly. For example, if a door or window is open while the system is disarmed, the control panel ignores the event. But, if a window is opened while the system is armed, it will immediately respond by sending a signal to your alarm monitoring center and triggering an audible alarm.

Alarm system panels have built in communicators that transmit and receive signals via a phone line. These signals are sent to a central alarm monitoring center where trained dispatchers monitor alarm system signals. In the event of a triggered alarm, a dispatcher will contact you to verify the emergency situation and if necessary, contact the police or fire station on your behalf.

Deter

An alarm panel responds to a triggered alarm by activating physical alarms such as a siren and/or strobe lights. These devices are used to scare an intruder away from your premises or alert you of a threatening situation such as a fire or the presence of carbon monoxide.

07/07/2014

Specials on alarms at Home Defence Security This week

While stock last