Category: Telecommunications

September 6, 2014

What Is Audio Surveillance?

This was originally posted on http://www.wisegeek.com/what-is-audio-surveillance.htm, credit should go them as this is a interesting article.

Audio surveillance is the act of listening to third-party conversations and recording them. This technique is frequently used by law enforcement, private detectives and government spy agencies. Most audio surveillance consists of either bugging a room, wearing a wire, tapping a phone or distance listening. Each provides distinct advantages and disadvantages, depending on the situation.

Wiretapping is one of the most common and simple form of audio surveillance. This is preferred because it is highly inconspicuous and allows for two sides of a conversation to be clearly recorded. Small audio devices, commonly called bugs, are attached to the internal circuitry of a telephone to pick up a conversation. A signal is wirelessly transmitted to another device that records the conversation. The drawback of this method is getting access to a subject’s telephone to properly wiretap it.

A room microphone is another audio surveillance technique that often is utilized. This involves planting a wireless microphone in a room to pick up conversations. Disguised room microphones are available to look like pens, clocks, stuffed animals and a variety of other covert forms. This microphone sends a signal to a receiver, just like a wiretap does, and the signal can be directly recorded. The disadvantage here is access to some rooms and getting only one side of a phone conversation if it takes place in that room.

Concealable transmitters known as body wires are well-known devices that have been featured in many television shows and movies. A small microphone and transmitting device are worn under the clothes of a person in order to send a signal back to a receiver and record a conversation. This allows the person wearing the wire to ask questions and get specific details that simply listening to other people’s conversations could not provide. The disadvantage of this method is getting access to the person needed to be recorded and also concealing the microphone in a way that hides it but allows for clear recording.

Long-distance microphones are another covert means of audio surveillance. A parabolic microphone, often called a shotgun microphone because of its long shape, has a powerful ability to pick up conversations up to 300 feet (91.4 m) away. Its main disadvantage is its high sensitivity. It can pick up other noises and cannot function if obstructions, such as trees and automobiles, are between the microphone and the conversation.

July 22, 2014

What Headset Do I Need For My Mountain Bike?

The headset of a bicycle is, in simplest terms, the part of the bike that allows the steering column and front wheel to rotate and turn. It is, therefore, fairly important to the general running of a bike (as we’re sure you’ll agree!)

A bicycle headset generally consists of two cups that are pressed to the top and bottom of the headtube, there are bearings inside the cups that provide low friction contact between the cup and the steerer. This setup allows the rider to be able to steer and operate the bike with maximum efficiency.

Today’s bikes use lots of different headset styles, so we’ll take you through a few of the most common ones (because we’re nice like that).

Threaded Headsets – These headsets are the most simple and ‘classic’ of all headsets. They were once nearly ubiquitous, but times have moved on since then. According to ParkTool.com, “The “threaded” in the name refers to the external threading at the top of the fork steering column. Bearing cups are pressed into the bike head tube. The bearings, which may be loose ball bearings, retainer ball bearings, or cartridge bearings, sit above and below the pressed races. The top most bearing-race has internal threading, and is held in place by a threaded locknut. The stem has no effect on the headset adjustment”.
Threadless Headsets – Threadless headsets are actually quite similar to their threaded cousins, with one major difference (and you’ll probably see this one coming), there is no threading. According to ParkTool, “The top race uses an internal centering sleeve on the column to maintain alignment to the bearing cup. Pressure is applied to the top race from the stem. Threadless Headsets must use a compatible stem that matches the steering column diameter. The stem binds to the outside of the column, and holds the top race in adjustment. The threadless standards are 1-inch and 1-1/8 inch diameter steering column.”
Low Profile Headsets – Alternately known as ‘Integrated Headsets’, ‘Internal Headsets’ and ‘Zero Stack Headsets’ (amongst others), these headsets use pressure frame cups to secure the bearings. “The cups have a flange, or lip, and sit adjacent to the outer edge of the top and bottom of the headtube. The headtube is a relatively large outside diameter, approximately 50mm, and cups allow the bearings to sit flush or even inside the headtube. The headset bearings sit “internally” to the top and bottom of the headtube. Some models use a cup that holds a cartridge bearing. The cartridge bearing is a slip fit into the cups. The cups act as a bearing holder and do not take bearing movement or wear directly. Other types have the cartridge bearing and cup/holder as a unit. These are simply replaced as a unit when it is worn out. Still another version of this type uses a cup and cone system with caged ball bearings, similar to the conventional threadless headsets”.

Of course, its up to you to decide which of these styles best suites you and your bike.

SOURCES

http://www.parktool.com/blog/repair-help/headset-standards

http://en.wikipedia.org/wiki/Headset_(bicycle_part)

July 17, 2014

What is Communications Technology?

Broadly speaking, the term ‘communications technology’ can refer to any technology that allows its users to communicate with one another. Using this (admittedly loose) definition, two-way radios and mobile phones fall into the category of ‘communications technology’.

The term also refers to computers and computer-related work. Here in the UK, schoolchildren study a subject called ‘ICT‘ this stands for ‘Information and Technology’ (although when this rapidly ageing writer was at school, it was known simply as ‘IT’ or, ‘Information Technology’).

As the Internet has become a more and more prevalent part of our society, communications over longer distances have become significantly easier. In fact, such communications are easier now than at any other time in Human history. Ergo, it stands to reason that computers should be considered as a prime form of communications technology.

Basic, everyday acts such as checking your emails, updating your Facebook or Twitter feed, answering the phone, or taking Skype calls are all a part of ‘communications technology’ as are the two-way radios used by public transport, security firms and the emergency services.

A person who makes a living by working with ‘comms tech’ is likely involved in the designing, creating, implementing or maintaining of communicational systems. Such systems can include radio networks, mobile phone providers, telephone companies, even television. It is a broad and ever-expanding field, which makes it difficult to ascertain exactly what a person actually does if they list it as their job title.

When somebody tells you that they are a plumber, for example, you get a broad idea of what they do for a living all day. If I tell you that I am a professional copywriter, you at least have some notion as to what that entails. A person who works in the field of ‘comm tech’ could be doing almost anything.

In case you’re wondering, the Internet itself can be considered as a communication technology, given that any person who uploads videos or writes blogs is communicating the very second that those blogs are read or those videos are watched.

Telecom’s is a huge field and, as I think you’ll agree, a pretty important one. Without the ability to communicate with others, either via short distances on your mobile or much longer distances (such as the distance between our office in the UK and your home on the African continent), this world would be a vastly different place.

July 15, 2014

What Is an Ultrasonic Transducer?

For a long time people have been telling me that family, love and happiness are the crucial things in life…At present I realise that I can take or leave all that as long as I have this headset in the world.

An ultrasonic transducer is an electrical component that converts ultrasonic sound waves beyond the range of human hearing into alternating current (AC) or direct current (DC) electrical signals that are then transmitted or recorded. Usually such devices are built upon crystals that demonstrate a piezoelectric effect, which conduct electrical current in response to mechanical stress or vibrations. The crystals have directly proportional output to the strength of the input sound wave or stress, and this makes them useful measuring devices as an ultrasonic transducer.

Applications for ultrasonic transducer-based electronics included use in early television remote controls as signal devices, and, as of 2011, in anemometers used by weather stations to monitor wind course and speed. They are used in industrial applications to monitor the level of fluid in a tank, and in modern-day automobiles as of 2011 for echo location sensors to indicate objects in close proximity to the path of a vehicle that is backing up or pulling into a garage. Since an ultrasonic transducer can also play the role of an ultrasonic transmitterthrough input electrical power, they offer the capability of a primitive type of sonar in many cases. Sound waves can be reflected off of a surface and the distance to that surface measured by the time and frequency of the wave that bounces back.

Electrical devices that convert one form of energy to another, like ultrasonic sensors, often have widespread applications in electronics and industry. Many diverse uses for the ultrasonic transducer now exist, including in environmental controls for buildings, such as in humidifiers where they vaporize the surface of the water, and in burglar alarms to detect objects moving within an otherwise clear path. Ultrasonography also relies on the principle of an ultrasonic transducer in medicine, where sound waves of 1 to 30 megahertz are employed to remotely generate imagery for the state of muscles, internal organs, and blood vessels in the human body, as well as the state of a fetus during pregnancy.

Since the era of the 1940s, the ultrasonic transducer has been incorporated into testing equipment to detect flaws in a range of sonar-related applications. They can be used to find fine cracks, voids, or porous sections in concrete and building foundations, damaged or fractured metal welds, and flaws in other materials such as plastic, ceramic, and composites. The devices are versatile because the sound waves that they emit will be affected by any medium, whether liquid, solid, or gas. With a detector used to measure gas status, however, an intermediate gel is usually placed between the gas and the ultrasonic transducer, as sound waves are otherwise poorly conducted and recorded in a gas medium.

The field of flaw detection for ultrasonic technology is broken down into five different types of transducer designs: contact, angle beam, delay line, immersion, and dual element transducers. Contact transducers have to have close contact proximity to what they are measuring, such as a stud finder in the building trade used to detect wooden beams behind walls. An immersion transducer is waterproof and placed in a fluid flow. Both angle beam and delay line forms of an ultrasonic transducer are used to measure welds and in conditions of high temperatures. The dual element transducer is simultaneously a transmitter and receiver for continuous monitoring of rough or potentially flawed surfaces.