Hominids started using primitive stone tools millions of years ago. The earliest stone tools were little more than a fractured rock, but approximately 75, years ago,  pressure flaking provided a way to make much finer work. Control of fire by early humans The discovery and utilization of firea simple energy source with many profound uses, was a turning point in the technological evolution of humankind. As the Paleolithic era progressed, dwellings became more sophisticated and more elaborate; as early as ka, humans were constructing temporary wood huts.
There are basically two kinds of videoconferencing and videophone systems: Dedicated systems have all required components packaged into a single piece of equipment, usually a console with a high quality remote controlled video camera. These cameras can be controlled at a distance to pan left and right, tilt up and down, and zoom.
They became known as PTZ cameras. The console contains all electrical interfaces, the control computer, and the software or hardware-based codec. There are several types of dedicated videoconferencing devices: Large group videoconferencing are built-in, large, expensive devices used for large rooms such as conference rooms and auditoriums.
Small group videoconferencing are either non-portable or portable, smaller, less expensive devices used for small meeting rooms. Individual videoconferencing are usually portable devices, meant for single users, and have fixed cameras, microphones, and loudspeakers integrated into the console.
Desktop systems are add-ons hardware boards or software codec to normal PCs and laptops, transforming them into videoconferencing devices.
A range of different cameras and microphones can be used with the codec, which contains the necessary codec and transmission interfaces. Most of the desktops systems work with the H. WebRTC Platforms are video conferencing solutions that are not resident by using a software application but is available through the standard web browser.
Solutions such as Adobe Connect and Cisco WebEX can be accessed by going to a URL sent by the meeting organizer and various degrees of security can be attached to the virtual "room". Often the user will be required to download a piece of software, called an "Add In" to enable the browser to access the local camera, microphone and establish a connection to the meeting.
WebRTC technology doesn't require any software or Add On installation, instead a WebRTC compliant internet browser itself acts as a client to facilitate 1-to-1 and 1-to-many videoconferencing calls. Videoconferencing modes[ edit ] Videoconferencing systems use two methods to determine which video feed or feeds to display.
Continuous Presence simply displays all participants at the same time,  usually with the exception that the viewer either does not see their own feed, or sees their own feed in miniature.
Voice-Activated Switch selectively chooses a feed to display at each endpoint, with the goal of showing the person who is currently speaking. This is done by choosing the feed other than the viewer which has the loudest audio input perhaps with some filtering to avoid switching for very short-lived volume spikes.
Often if no remote parties are currently speaking, the feed with the last speaker remains on the screen. Echo cancellation[ edit ] Acoustic echo cancellation AEC is a processing algorithm that uses the knowledge of audio output to monitor audio input and filter from it noises that echo back after some time delay.
If unattended, these echoes can be re-amplified several times, leading to problems including: The remote party hearing their own voice coming back at them usually significantly delayed Strong reverberationwhich makes the voice channel useless Howling created by feedback Bandwidth requirements[ edit ] Deutsche Telekom T-View ISDN type videophone meant for home offices and small businesses with a lens cover which can be rotated upward to assure privacy when needed Broadband Internet access Videophones have historically employed a variety of transmission and reception bandwidths, which can be understood as data transmission speeds.
Data transfer rates and live video image quality are related, but are also subject to other factors such as data compression techniques. Some early videophones employed very low data transmission rates with a resulting poor video quality.
Broadband bandwidth is often called "high-speed", because it usually has a high rate of data transmission. Such devices need to route calls through a Video Communication Server to be able to reach H. In addition, an attractive factor for IP videoconferencing is that it is easier to set up for use along with web conferencing and data collaboration.
These combined technologies enable users to have a richer multimedia environment for live meetings, collaboration and presentations. The organization's vision is to maximize the interoperability of UC based on existing standards.
A number of call-setup methods based on instant messaging protocols such as Skype also now provide video. Another protocol used by videophones is H.
Videophones that work on regular phone lines typically use H. A slightly modified version of H. It applied mostly to dedicated circuit-based switched network point-to-point connections of moderate or high bandwidth, such as through the medium-bandwidth ISDN digital phone protocol or a fractionated high bandwidth T1 lines.
Modern products based on H. While additional software is required to patch together multiple video feeds for conference calls or convert between dissimilar video standards, SIP calls between two identical handsets within the same PBX were relatively straightforward. Many in the industry have encountered both types of interfaces, and normally graphical interfaces are encountered on a computer.
User interfaces for conferencing have a number of different uses; they can be used for scheduling, setup, and making a videocall. Through the user interface the administrator is able to control the other three layers of the system. Conference Control performs resource allocation, management, and routing.
This layer along with the User Interface creates meetings scheduled or unscheduled or adds and removes participants from a conference. These signals control incoming and outgoing connections as well as session parameters.Dear Twitpic Community - thank you for all the wonderful photos you have taken over the years.
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