CCTV Camera/ Device Installer Interview Questions And Answers

IP cameras require a network only for them. Otherwise they gonna reduce the system’s performance. Also, it is a more complicated technology to deal with. It requires a little bit of knowledge in Network Systems in order to make it work well.

Charge Coupled Device, CCD, is one of the two main types of image sensors used in security cameras. When a video is recorded, the CCD is struck by light coming through the camera's lens. Each of the thousands or millions of tiny pixels that make up the CCD converts this light into electrons. The number of electrons, usually described as the pixel's accumulated charge, is measured, and then converted to a digital value. This last step occurs outside the CCD, in a camera component called an analog-to-digital converter.

Low frequency light below the visible spectrum. Infrared is used in surveillance cameras to provide a light source to record images in dark and zero light conditions.

The Motion Picture Experts Group (MPEG) released MPEG-4 encoding in 1998. The basic idea behind MPEG is that compressed images are compared before being transmitted over the network. The first compressed image is used as a reference and compared to the images that follow it in the video sequence. The first image is transmitted over the network along with the parts of the following images that differ from the initial reference image. The viewing application on the receiving end of the transmission then reconstructs all images based on this information and displays the result. This is a simplified description of how MPEG-4 works.

A pixel refers to an individual area on the surface of the imaging device, normally a CCD. It is made from photosensitive material which converts light into electrical energy. In the context of a display monitor, a pixel is also referred to as an individual area on the surface of the screen which converts electrical energy to visible light.

A WDR security camera (Wide Dynamic Range) is used for capturing clear images of objects surrounded by a strong back light, while still keeping the background visible.

☛ Analog -> Goes up to 1000 TVL
☛ AHD -> Analog High Definition – 720p resolution
☛ CVI/TVI -> Different Manufactures. Both are 1080p resolution.
☛ SDI – Full High Definition – 1080p
☛ IP -> Network cameras.

A Video Balun enables the transmission of video using unshielded twisted pair wire instead of coaxial cable. The word "balun" comes from combining the terms balanced and unbalanced. The function of a balun is to transform an unbalanced signal into a balanced signal. When video signal is transmitted through coaxial cable, the distance traveled by the signal is limited because the signal is in the form of an unbalanced signal that is susceptible to Radio Frequency Interference or noise. Coax cable incorporates special shielding to minimize noise. Video Baluns transform the video signal into a balanced form in which each wire in the twisted pair transmits an identical signal with opposite polarized magnetic fields. Noise affects each signal equally. When the signals are combined, the noise is cancelled out. By using a designed balun, an unshielded twisted pair wire can transmit video for much longer distances than coax cable and with a lower cable cost.

A quality brand of DVR Cards made for Windows based computers.

This is a device that takes inputs from 2 or more video channels and combines them into one signal. This is often done by using time division multiplexing, which interleaves frames from each channel in such a way that they can be split out again. Frequency division multiplexing uses different frequencies to achieve the separation of the signals.

RS-232 is a communications standard for serial communications between devices. In CCTV, this can be communication between a contoller and a surveillance camera. The RS-232 standard allows for the connection of two devices through a serial link, and is the protocal used for serial connections in computers. RS-485 allows for serial connections between more than 2 devices on a networked system and is defined below.

This refers to a type of lens that has the capability to change the focal length. This allows adjustment of the magnification and field of view of the security camera.

Analog DVR’s: I watch DVR
AHD DVR’s: I watch DVR
SDI DVR’s: I watch DVR
IP NVRS: I watch NVR
TVI DVR’s: For Karbontech: Super Live Pro or I watch DVR (Depending on the DVR model). For Hikvision: IVMS 4500
CVI DVR’s: Dahua DVR – IDMSS (Apple Cellphones) and GDMSS (Android Cellphones).

BNC is a connector for coaxial cable that is most commonly used for CCTV installations.

Gamma correction controls and adjusts the overall brightness of an image for consistency.

This refers to the part of a video signal that carries the monochrome information. i.e. brightness information.

This is the ratio between the signal strength and the noise levels on an audio or video signal.

The mechanical device that adjusts to vary the amount of light passing through the lens of a camera.

All technologies can be installed using cat5, cat6 or over coax (Siamese cable). Exception made for IP cameras that require a Cat5 or Cat6 installation.

The total opposition offered by a device to the flow of an alternating current. Measured in Ohms.

A method of displaying set-up information and/or instructions on a display monitor.

This is a measure of the resolution of a video device. The higher the number, the higher the resolution is. 380 TVL is considered medium resolution. 480 TVL or greater is considered high resolution.

Devices with internal sync have an internal crystal to provide sync pulses without needing reference from any external device.

Digital video pictures can be compressed with a number of techniques. These include: JPEG and JPEG-2000 (for still images), M-JPEG and MPEG (for moving pictures).

Technology used for flat screen displays.