algorithm - A formal set of instructions that can be followed to perform a specific task, such as a mathematical formula or a set of instructions in a computer program. In compression software, refers to a specific formula used to compress or decompress video or other data.

digital spread spectrum (DSS) technology - the most common and easiest explanation to understand involves frequency hopping -- instead of transmitting on one frequency, a spread spectrum system switches rapidly from one frequency to the next. The choice of the next frequency is random, so it is nearly impossible for someone to eavesdrop or jam the signal. Spread spectrum has been recently combined with digital technology for spy-proof and noise-resistant communications.

DSS provides:

• Longest range - 900-MHz microphones all have a better range due to the wavelengths being shorter -- shorter waves are easier to bounce off objects.

• Best sound quality - Since the spread spectrum signal is uniformly spread over a wide range of frequencies for transmission, the signal avoids interference and noise from other signals.

• Highest security - Due to digital transmissions and constantly changing frequency channels in use, only the matching receiver has a copy of the pre-assigned spreading code. Millions of scrambling codes are available and are selected automatically.

encryption - Encryption is the conversion of data, using a mathematical algorithm, into a form that cannot be read by unauthorized users. Authorized users must be provided with a decryption key in order to unscramble the information. There are different strengths of data encryption, determined by the length (in bits) of the key used. In general, the longer the key, the stronger the encryption, the more secure the data.

firewall - A combination hardware and software buffer that many companies or organizations have in place between their internal networks and the Internet. A firewall allows only specific kinds of messages from the Internet to flow in and out of the internal network. This protects the internal network from intruders or hackers who might try to use the Internet to break into those systems.

LAN - local area network: a local computer network for communication between computers; especially a network connecting computers and word processors and other electronic office equipment to create a communication system between offices

Lux - a unit of illumination equal to the direct illumination on a surface that is everywhere one meter from a uniform point source of one candle intensity or equal to one lumen per square meter : Note: lower LUX value Cameras work better in low light

MD5 hash - MD5 is a one-way hash algorithm that takes any length of data and produces a 128 bit "fingerprint" or "message digest". This fingerprint is "non-reversible", it is computationally infeasible to determine the file based on the fingerprint. This means someone cannot figure out your data based on its MD5 fingerprint.

metadata - Data about the data, that is, the description of the data resources, its characteristics, location, usage, and so on. Metadata is used to identify, describe, and define user data.

MPEG-4 compression - The simple definition of compression is the reduction of file size by removing redundant or non-vital data. All video is compressed to some level when it is digitized with the difference between compression levels being distinguishable by quality and/or file size.
Standard MPEG 2 compression (typically used on DVD and satellite TV) operates at 15-25 Mbps (mega bits per second), which translates to 7-11 GB per video hour. These values are prohibitive for in-car applications. For the typical stream size coming from an in-car camera, MPEG-2 would either be big, or not provide the quality required and MPEG-1 would produce an inferior, small grainy picture. L-3 Mobile-Vision has chosen MPEG-4 because it provides the highest quality video in the least amount of memory.

pre-event recording – when the digital video recorder is on, it is constantly capturing images and putting them in temporary memory. When a trigger is received, the unit starts recording to the compact flash card, but it can also grab images captured before the trigger (from temporary memory) and store them. The Flashback system allows the user to set that capture time for any amount up to 60 seconds

RAID (redundant array of independent disks) – is a way of storing the same data in different places (thus, redundantly) on multiple hard disks. By placing data on multiple disks, input/output operations can overlap in a balanced way, improving performance. Since multiple disks increases the mean time between failure (MTBF), storing data redundantly increases fault-tolerance

solid-state – No moving parts. Solid-state memory, in contrast to hard disks with several moving parts, is inherently more durable.

TRACE – feature available on the Flashback DVR which allows the user to mark the video record while it is recording. This is a powerful tool for recovering discarded evidence that is disposed of while in pursuit – an officer can press the TRACE button when the action is taking place, and because the Flashback DVR includes an internal GPS receiver, the GPS coordinates are recorded at each TRACE marking. Later, the officer can quickly “return to the scene” to search and recover the evidence.