tailieunhanh - Practical TCP/IP and Ethernet Networking- P46

Practical TCP/IP and Ethernet Networking- P46: The transmitter encodes the information into a suitable form to be transmitted over the communications channel. The communications channel moves this signal as electromagnetic energy from the source to one or more destination receivers. The channel may convert this energy from one form to another, such as electrical to optical signals, whilst maintaining the integrity of the information so the recipient can understand the message sent by the transmitter | The Internet for communications 207 Internet phone release 5 Internet Phone by VocalTec enables PC users to make regular full-duplex telephone calls over the Internet to any other Internet connected PC in the world providing the caller signs up with an internet telephony provider ITSP which supports the VocalTec system. As is the case with FreeTel functions include some of the amenities of a full-featured telephone such as caller ID call waiting muting and blocking. In addition to this it is possible to introduce live motion video which enables the recipient to actually see the caller without additional hardware required. It also supports audio conferencing with up to 100 people white boarding which enables the sharing of documents photos and drawings with other users and text chatting via the PC keyboard. Netspeak web phone Like Internet phone Netspeak Webphone offers voice video and data communications over the Internet and any other TCP IP-based networks with all the functions of a top-of-the range conventional telephone as well as videophone support using the standard. WebPhone uses TrueSpeech GSM voice compression as used in cellular phones to overcome the bandwidth limitation inherent to Internet communication. PC to phone Net2Phone Net2Phone is an innovative software product system from IDT. Net2Phone is a service that allows the user of an Internet connected multimedia PC or laptop to place calls from anywhere in the world to any regular phone in the world using a dedicated Internet exchange in the USA. Users are not limited to PC-PC technology which requires both users to have access to multimedia PCs and to be connected to the Internet at the same time either by coincidence or prearrangement. Only the caller needs a PC with an Internet connection and can use any ISP in order to make the call. The cost of calls varies but is on average less than 10 of a normal phone call. In addition to this calls to any 1-800 number in the .