Page 107 - DCAP303_MULTIMEDIA_SYSTEMS

Unit 6: Hardware

the adapter to a LAN. Using such an ATA, it is possible to connect a conventional telephone to notes
a remote VoIP server. The ATA communicates with the server using a protocol such as H.323,
SIP, MGCP, SCCP or IAX, and encodes and decodes the voice signal using a voice codec such as
G.711, G.729, GSM, iLBC or others. Since the ATA communicates directly with the VoIP server, it
does not require a personal computer or any software such as a softphone. It uses approximately
3 to 5 watts of electricity, depending on model and brand.

purpose
An ATA is connected between an IP network (such as a broadband connection) and an existing
telephone jack in order to provide service nearly indistinguishable from PSTN providers on
all the other telephone jacks in the residence. The ATAs are used by many VoIP companies
selling a telco-alternative VoIP service, where the device is used to replace a user’s connection
to a traditional telephone company. When sold in connection with a VoIP service, the ATA is
often locked so it cannot be used with a competing service, and the user can only partly change
its configuration. Some providers do sell devices that are not locked and can be used with any
compatible provider. This type of service, which is fixed to one location, is generally offered by
broadband Internet providers such as cable companies and telephone companies as a cheaper
flat-rate traditional phone service.
6.2.5 Universal serial Bus (UsB)
The Universal Serial Bus (USB) is a standard for a wired connection between two electronic devices,
including a mobile phone and a desktop computer. The connection is made by a cable that has a
connector at either end. One end, the one that plugs into the computer, is the same across all USB
cables while the one that plugs into the mobile device can be of various types such as miniUSB,
microUSB or a proprietary connector.

The USB version 1.1 provides maximum speeds of up to 1.5 MB/s while the current version 2.0
is about 40 times faster. The versions are backwards compatible and the speed is limited by the
slower device. Transferring data may require drivers to be installed on the desktop computer
but some phones offer “mass storage” mode which means they appear as thumb drives to the
computer and no special drivers are needed.
The USB is an industry standard developed in the mid-1990s that defines the cables, connectors
and protocols used for connection, communication and power supply between computers and
electronic devices.
The USB was designed to standardize the connection of computer peripherals, such as keyboards,
pointing devices, digital cameras, printers, portable media players, disk drives and network
adapters to personal computers, both to communicate and to supply electric power. It has become
commonplace on other devices, such as smart phones, PDAs and video game consoles. The USB
has effectively replaced a variety of earlier interfaces, such as serial and parallel ports, as well as
separate power chargers for portable devices.
Upto 2008, about 2 billion USB devices were sold each year, and approximately 6 billion devices
were sold in total.
In addition to their data transferring application, USB cables also carry an electric charge that can
be used to power peripherals (such as USB mice or keyboards), and many mobile phones can be
charged through their USB port.
UsB 1.0

• USB 1.0: Released in January 1996.
• Specified data rates of 1.5 Mbit/s (Low-Bandwidth) and 12 Mbit/s (Full-Bandwidth).
Does not allow for extension cables or pass-through monitors (due to timing and power
limitations). Few such devices actually made it to market.

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