How do I choose the correct camera for my application?
This in general is a comparatively difficult decision. Many aspects of the installation must be taken into consideration in order to obtain the correct performance that meets your requirements.

A high resolution camera should be considered where greater detail of scene is required. E.g. Colour 460 TVL, Monochrome 570 TVL. Choosing a more sensitive camera will improve reproduction in poorly lit areas. The sensitivity of a camera is indicated by the minimum amount of light in order for the camera to produce a usable picture. e.g. Colour 1.0 Lux at F1.2.

A conventional camera produces a pale backdrop when an object is shot against a bright background. BLC (Back Light Compensation) will counter strong light sources retaining picture quality.

Concentrated light sources directed towards the camera (e.g. car head lamps) can be inverted by an optional peak white inverter or an eclipser function. This has the effect of bringing detail to areas and making an object clear, that would otherwise be shadowed.
How do I set up a camera and lens for use in Low Light conditions and or with Infra Red Lighting?
Access controls allow individuals and Property Managers track users of the system with real-time reports. Time schedules can be developed and maintained for a totally controlled environment. If the access system is designed by a professional it should stop or at least slow down unauthorized entry and thus minimize the potential for crime.
How can installing an Access Control System save time and money?
The answer to this is the same as that for questions relating to Back Focusing on Page 31 and 34, with the addition of the following:

When setting the back focus of a Colour camera for low light conditions you should place an ND1 (Neutral Density) filter in front of the lens. When setting the back focus of a Mono camera for low light conditions you should place an ND3 (Neutral Density) filter in front of the lens. When setting the back focus of a Mono camera fitted with I/R lighting for low light conditions you should place an IRP (Infra- Red Pass) filter in front of the lens.
Should you not have any of the above filters you may have to attend site during the hours of darkness.
I have installed a new camera and lens why am I unable to obtain a sharp image?
The most common resolve to this is to ensure that both camera and lens are the same mount i.e. ‘CS’ mount lens on a ‘CS’ mount camera and a ‘C’ mount lens on a ‘C’ camera.
What are OSD cameras?
OSD (On Screen Display) cameras have a menu system within the camera assembly that can be accessed in order to set functions such as Iris levels, AGC on/off and most features of standard and advanced cameras.
Why do I have a clear sharp picture during the day and it is out of focus at night?
This is due to the depth of field changing as the light conditions change and can be easily overcome by following set procedures.
When can I use a manual iris lens?
A general rule of thumb is only to use a MI lens in an internal application. This is because you are reliant on the electronic circuitry of the camera compensating for light changes in the scene and this is not able to compensate to the same degree as that of an Auto Iris lens.
How do I back focus a camera fitted with a fixed focal length lens?
This is achieved by following five simple steps:
• Set the physical focus of the lens to infinity (clockwise from the front).
• Aim the camera at the subject to be viewed.
• Release the camera back focus mechanism.
• Adjust the back focus to obtain the best possible picture.
• Secure the cameras back focus mechanism.
What size monitor should I be using?
The correct size monitor is dependent on its use e.g. the number of images to be displayed at any given time, the viewing distance and the available space.
What is Video Termination?
This is the end of line resistance of any CCTV system and this should be set to 75 ohm. Should you encounter any double image or ghosting this is more often than not caused by two pieces of equipment in series both having the 75-ohm switch set on. Only the last piece of equipment should be set at 75-ohm.
What camera housing should I use and at what IP Rating?
Camera housings come in various shapes and sizes. With regard to the correct IP rating protection, this will range from dust and water ingress. This system is governed by a number of European and British standards.

• Protected against dust - limited ingress.
• Protection against low pressure jets of water from all directions – limited ingress permitted.

• Protection against dust - no ingress. • Protection against low pressure jets of water from all directions – limited ingress permitted
• Protection against high pressure water from all directions - limited ingress permitted.
What is the difference between simplex and duplex multiplexers?
Video multiplexers are designed to allow recording of several cameras onto one recorder.

A simplex machine is best suited to applications where recording only is the priority. Simplex machines cannot display multi screen images (i.e. quad, 9 way and 16 way split) while in the record mode.

If an operator is monitoring the system (i.e. security guard) then a duplex machine is more suitable. A duplex machine can provide screen splits and user selectable images without affecting what is recorded onto the recorder. Should you use two recorders, it becomes possible to record and playback simultaneously.
What is the difference between Standard VHS and SVHS recordings?
In general the main difference apart from cost is the increase in overall resolution. A standard VHS machine may achieve in the region of 300 TVL (mono) whereas S-VHS machines may achieve in the region of 400 TVL. However this being achieved will depend on the correct ancillary equipment being used.
Which pan and tilt unit should I use?
The choice is wide and varied dependent on the system requirements. You may require Top mount, Side mount, 230V AC or 24V DC to name just a few.

• Pro: Can fit two IR lamps on the side of the Pan/Tilt. These act as a counter balance enabling you to use a lighter duty Pan/Tilt head.
• Pro: Compact size.
• Con: Restricted tilt often -45 to 0 dependent on the housing fitted.
• Con: Cannot be inverted.

• Pro: Can be inverted.
• Pro: Often cheaper.
• Pro: Large tilt often +or- 180
• Con: Difficult to mount IR lamps.
• Con: Generally large size.
What type of illumination can I use with colour cameras?
Only lighting within the visible wavelength should be used with colour cameras. Tungsten Halogen is often the recommended source of lighting.
Can I use I/R Lamps with colour cameras?
The answer to this is a definitive NO. Colour cameras are typically fitted with an IR cut filter and will not allow IR light in excess of 700Nm to pass resulting in the camera performing poorly in these circumstances.
What is an ISDN Telephone Line?
An ISDN (Integrated Services Digital Network) Line is a digital system allowing a camera to be updated at a rate of 15 frames a second.
What is a PSTN Telephone Line?
A PSTN (Public Switched Telephone Network) Line is an analogue network allowing a camera image to be updated every few seconds and is therefore slower than that of an ISDN network.
What is an ADSL Line?
Also known as Broadband, an ADSL (Asymmetric Digital Subscriber Loop) line is a form of Digital Subscriber Line in which the bandwidth available for downstream connection is significantly larger than for upstream. Although designed to minimise the effect of crosstalk between the upstream and downstream channels this setup is well suited for web browsing and client-server applications as well as for some emerging applications such as video on demand..
What is a Leased Line?
Leased Line, sometimes known as Kilostream, Megastream or Private wire. This is NOT a dial up line but is connected 24hrs a day and is usually subject to an installation charge and a quarterly bill.
What is full picture update?
Full picture update is a technology that enables a transmission system to update a high quality full picture refresh at very fast speeds.
Do I have to use a Regulated Power Supply?
In general the answer is yes. Most manufacturers will recommend the use of such power supplies as standard with their equipment. You should always consult the manufacturers specifications prior to the connection of any power supply.
What is the maximum distance I can run 12vdc when powering a camera?
This is a commonly asked question and there is no simple answer. Some manufacturers may recommend that their cameras can be run over (X) distance with (Y) cable. This however should still be considered as a general guide. Cable conductor size and installation route must also be taken into consideration. If you are unsure, we would recommend that you contact Technical Support for guidance.
What is the difference between RG59 and URM70 Coax?
In general there is little difference. However RG59 is a hard drawn conductor and is best suited to fixed camera installations. URM70 has a multi stranded centre conductor and is more suited to installations such as PTZ cameras.
What is a ground loop?
An AC current that can be produced in a cable. This is usually caused by parts of the system being fed from different electrical sources resulting in different earth potentials at each end. The result is interference on the signal, usually in the form of dark bands across the monitor and on occasion tearing in the top third of the image.
How can I eliminate ground loop faults?
This can be achieved in a number of ways, the easiest of which is the installation of a Ground Loop Isolation Transformer. This is best installed at the monitor or recording end of the system.
What is the correct level for a video picture?
The correct level is 1 volt peak to peak. This can only be accurately set either with an oscilloscope or with a video level meter.
How often should I replace my video tapes?
In general it is recommended that all video tapes should be replaced after a period, no greater than 20 passes of each tape. That being 10 record and 10 play back. This will also be dependent on the quality of tape being used and that the recording equipment is in good operational condition.
Manual or Auto Iris Lens?
The iris is the part of the lens that determines how much light falls upon the camera CCD sensor. The Manual Iris 'MI' lens has this fixed at the time of installation. As the light levels change in the scene, the lens can do nothing to prevent either too little or too much light entering the camera. Virtually all cameras employ an Automatic Electronic Shutter 'AES' to compensate for these variations when fitted with an MI lens. However they are only able to cope with a relatively small change in light levels.

An MI lens should never be used in an external situation, as the camera will be unable to cope with large changes in light levels. Use an Auto Iris ‘AI’ lens in this case, or indeed anywhere where large scene illumination changes take place.

The advent of new sensor technology such as PIXIM may result in a change to this situation in the future.
What features should I look for in a CCTV Digital Video Recorder (DVR)?
All DVRs are definitely not made equal! There are several factors that are critical to consider when purchasing a DVR, especially when comparing price. The most important factors to look at are the number of cameras supported, frames per second (fps), compression technology, hard drive space, network connection / remote viewing capability, motion detection, scheduling, and ability to save video and audio to a CD or flash drive. You should also look for easy and comprehensive search capabilities and audio support. The setup and user interface should be intuitive and easy to operate.
What is frames per second?
The frames per second (fps) relates to how many pictures the DVR will record in a second. Real time recording is about 30 fps on each camera. To calculate the fps per camera take the total fps in the system and divide it by the number of video inputs. For example, a 60 fps digital video recorder with 4 video inputs would result in about 15 fps per camera. The technology has finally gotten to the point now where real time recording is affordable. If you are recording cash registers or something similar then you should definitely invest in real time recording.
How big a hard drive do I need?
The amount of hard drive space is very important because it will limit how many days of recording you can store before the system has to start recording over the oldest video. Each DVR will have its storage capacity listed in the specifications. But this calculation is just a rough estimate as there are many factors that affect hard drive use. The most critical factor being the compression format used by the DVR (for more info on compression formats click here). But also the type of cameras that are connected to the DVR make a difference (specifically the chip size and resolution) and also the features that are selected on the DVR. If you use the scheduling or motion detection features or tune down the frame rate that will extend the storage capacity of the unit. Even the field of view (what you are recording) will affect the storage capacity - the more complex the image, the more hard drive space it will take to capture the complexity.
What is the difference between a PC-based DVR and an Embedded DVR?
A PC-based digital video recorder is basically a personal computer that has been modified with hardware and software to work as a DVR. An embedded digital video recorder is a machine that has been manufactured specifically to work as a DVR. In embedded DVRs there is typically one circuit board with software burned into the chip.
There used to be significant differences in features between the PC-based and the embedded machines. But with recent advancements in the embedded DVR technologies the differences are becoming less. The advantages of an embedded digital video recorder is that they are extremely stable and reliable since they contain fewer parts. The software is often written in basic machine code or Linux code which tends to be more stable than Windows software. The advantages of the PC-based digital video recorders is that they are easier to interact with because you use the on-screen menus and a mouse (as opposed to embedded which you interact with more like a VCR - via buttons). And you tend to have more features and options on the PC-based machines.
How does a CCTV digital video recorder work?
A CCTV digital video recorder (or “DVR” for short) is essentially a computer that saves security video images to a hard drive. Most security cameras in use today capture an analog picture. The DVR converts the analog signal to digital and then compresses it.
Many cameras can be connected to one DVR. DVRs generally come with 4, 8, or 16 camera inputs. The DVR will allow you to view all of these images at once or one at a time, and all of the video is saved to the hard drive. Additional switches, quads, or multiplexors are not required.
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