System information

Hardphones, Softphones, and ATAs
There are three types of endpoints you would typically provide your users with that
could serve as a telephone set. They are popularly referred to as hardphones, soft-
phones, and Analog Terminal Adaptors (ATAs).
A hardphone is a physical device. It looks just like an office telephone: it has a handset,
numbered buttons, etc. It connects directly to the network, and it’s what people are
referring to when they talk about a VoIP telephone (or a SIP telephone).
A softphone is a software application that runs on a laptop or desktop. The audio must
pass through the PC’s sound system, so you normally need a headset that will work
well with telephony applications. More recently, softphone applications have been
written for smart phones that allow you to connect to other networks other than just
the cellular network. The interface of the softphone is often styled to look like a physical
telephone, but this is not necessary.
An ATA is designed to allow traditional analog telephones (and other analog devices,
such as fax machines, cordless phones, paging amplifiers, and such) to connect to a SIP
network,
‡
and will typically be a sandwich-sized box that contains an RJ-11 connector
for the phone (commonly referred to as an FXS port), an RJ-45 connector for the net-
work, and a power connector. Some ATAs may support more than one phone.
Hardphones have the advantage that the handsets have good acoustic properties for
voice communications. Any decent-quality telephone is engineered to pick up the fre-
quencies of the human voice, filter out unwanted background noise, and normalize the
resulting waveform. People have been using telephones for as long as the telephone
network has existed, and we tend to like what is familiar, so having a device that com-
municates with Asterisk using a familiar interface will be attractive to many users. Also,
a hardphone does not require your computer to be running all the time.
Disadvantages to hardphones include that they are nonportable and expensive, relative
to the many quality softphones on the market today that are available for free. Also,
the extra clutter on your desk may not be desirable if you have limited work space, and
if you move around a lot and are not generally at the same location, a hardphone is not
likely to suit your needs (although, one at each location you frequent might be a valid
solution).
Softphones solve the portability issue by being installed on a device that is likely already
moving with you, such as your laptop or smart phone. Also, their minimal cost (typi-
cally free, or around the $30 price range for a fully featured one) is attractive. Because
many softphones are free, it is likely that the first telephone set you connect to Asterisk
will be a softphone. Also, because softphones are just software, they are easy to install
and upgrade, and they commonly have other features that utilize other peripherals, like
‡ Or any other network, for that matter. ATAs could more formally be said to be analog-to-digital gateways,
where the nature of the digital protocol may vary (e.g., proprietary ATAs on traditional PBXs).
86 | Chapter 5: User Device Configuration
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