USB Memory

USB Memory

Tired of switching CD/DVD discs while backing up? Flash USB drives is the answer to rescue your data!

If you already backup often, you are doing the most you can to secure your files against accidental file deletion and recovery, file damage and what not. So CD, DVD and flash USB drives are considered.

Here is when a flash USB drive comes handy. It not only allows faster data copying than CD or DVD, but can also admit from 256Mb to 4Gb of data (or maybe more). Moreover, you can take the USB drive with you anywhere you go and transfer the data between distant computers without resolving to FTP backup.

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Ultrasonic Detectors

Ultrasonic Detectors
by: James Morgan

Let's cover ultrasonic detectors. The term ultrasonic denotes sound frequencies that are above the range of human hearing, the upper limit of which is 16 kHz in healthy people in their twenties. The frequencies used in ultrasonic detectors vary between different models, ranging from 23 to 40 kHz. The frequency is generated by an electronic oscillator and is fed to one or more loudspeakers. These need to be very small, smaller in fact than the tweeter in a hi-fi loudspeaker, because the moving parts must move very rapidly and so their mass must be kept to a minimum. This is an advantage of an ultrasonic detector alarm system as the units can then be made small and unobtrusive. The same unit contains a microphone with amplifying and processing circuits.

Ultra-high frequency sound is thus projected into the protected area of the ultrasonic detector. Some of it is received directly by the microphone from the loudspeaker, while some is picked up after being reflected from walls and objects in the room. When there is no movement, both direct and reflected sounds are of the same frequency. Should movement of an object occur, the sound reflected from it will undergo a change of frequency owing to the Doppler Effect. Thus the ultrasonic detector microphone now picks up two frequencies: the original received directly from the loudspeaker, and the shifted frequency reflected from the moving object.

If two different frequencies are mixed, the result is that a third one appears that is the difference between the two. When the two frequencies are close, the third is often termed a beat note. The effect can sometimes be heard when two internal combustion engines are idling at slightly different speeds: the beat note is heard by the ultrasonic detector as a throbbing sound that varies in frequency as the speed of one or other of the engines changes.

The processing circuits in the ultrasonic detector detect the presence of the beat note and actuate the output relay which is of normally closed type. The ultrasonic detector can thus be connected into a normal loop, but it is preferable for space detectors to be connected to a separate zone from the perimeter sensors so that rapid identification of the alarm source can be made. A power supply of 25 - 50 mA is required from the control box.

Ultrasonic detectors usually have a range up to 30ft, but they have a sensitivity control which can reduce the range down to about 10 ft. The polar pattern is in the form of a narrow lobe and so the device affords little protection at the sides. It should therefore be pointed towards the expected point of entry. As the Doppler Effect is greatest for forward or backward motion, the sensor is more sensitive to these than to side-to-side movements. This is another reason to mount the ultrasonic detector facing the possible point of entry.

Check Your Office Security

Check Your Office Security
by: Andrew Stratton

A criminal activity can take place at any place and at any time, whether it is a home or an office. However, the advancement in technology has put an end to these unwanted activities. This has been made possible by making the use of hidden cameras or spy cameras. These keep a check on every movement of employees and trace the culprit at the time of any problem in an organization.

However, with people getting self-centered and the world becoming materialistic everyday, these cameras have become a necessity for every organization. Also, spy cameras will help in keeping a watch on those employees who waste their time in trivial personal activities. This is because they will be aware of the fact that someone is keeping an eye on them and any carelessness on the work front can lead them to trouble.

These cameras can also speed up the process of investigation of any case and save the precious time and efforts of the intelligence agencies. The tapes recorded in these spy cameras can also be produced in the court as a strong proof against the culprit. Moreover this is a common technique used in departmental stores to make sure that no customer takes the products without paying the bill.

The spy cams are hidden at places unnoticeable by an organization. Any unusual activity in the office hours can easily be detected on these cameras. This helps in maintaining a discipline in the office. Sometimes they also give an indication of any unwanted activity to be occurred in future and aid in averting the same. Furthermore, spy cameras ensure the safety of an individual’s precious possessions in his absence. Stealth camera is a kind of hidden camera which also has an in-built recorder. These can be put in a vault and even if the loss is unavoidable the culprit can be traced.

There are various advantages of these cameras. The hidden cameras or spy cameras are operative in varying conditions of light. There isn’t any distortion in the picture quality irrespective of the light. These are very useful at high security areas, such as airports, hotels and embassies. These are compressed and tactful cameras and have specially been designed so that they can be easily hidden. The finest quality spy cams can be purchased at low prices too.

Thus, spy cameras are more of a necessity for an organization than a preferred choice.