VoIP

VoIP, or Voice Over IP, is the generic term for transmitting and routing voic e (or other audio, such as Fax transmissions) over IP networks.

My main interest in VoIP is to test a system from my home to my dorm where I live during the week, and eventually perhaps move to all network-based VoIP "hardphones" (dedicated telephones that plug into a network and only operate on VoIP, as opposed to analog "POTS" (Plain Old Telephone Service/System)). This would not only allow free calling between locations (assuming adequate bandwidth) but would also allow automatic routing of analog calls (via an interface card) to any extension. This would, of course, require a dedicated server, most likely running Asterisk, a free (both in terms of beer and speech) and open-source software PBX.

Hardphones and Extensions

In addition to just getting experience with VoIP, I would really love the ability to route calls between any phone in my house, at work (at any of my offices), and my dorm. With the use of an Asterisk server, this would be easily possible, in addition to tieing in to the POTS landlines at all of those locations.

Wireless VoIP

While still in the development phases (I know of few if any working units, and none that are inexpensive), I would love to be able to obtain a WiFi (WLAN) VoIP handset which would automatically connect to the nearest wireless network (either unsecured or secured with authentication setup), announce its presence to the Asterisk service (or maybe VPN in), and make itself available for calls.

Possible Hardware

Hitachi IP5000
WIP330 - has a web browser and runs Windows CE.
D-Link DPH-540 - Flip-style WiFI VoIP phone

And a larger list available from VoIP-info.org here

Automatic Ringdown

One of the things that really piques my interest about VoIP is that the Asterisk server can (theoretically, I believe) detect when any given phone comes off-hook (handset is picked up) and perform an action. Being that I act in a SysAdmin capability at multiple sites, this would enable a number of possibilities involving an automatic ringdown. Automatic ringdown is a term from analog (POTS) phone service, also known as a "hot line", where two phones are tied directly together. When one handset is picked up, the other immediately rings, and a direct connection is established once the second end is picked up. Traditionally, this was done with a simple circuit (which can be purchased from many electronics sources) called, imaginatively, a ringdown converter.

Theoretically, this could be implemented in a VoIP-based system allowing:

• A direct hotline between my office/server room and remote locations
• With some scripting on Asterisk to monitor where I currently am, a direct hotline from my server locations at home, the dorm, and some other locations to whatever phone I am closest to.

Cisco implements this technology, calling it Private Line Automatic Ringdown (PLAR).

VoIPinfo.org has a short stub on implementing this feature located Here.

External Links

VoIP-info.org - A great site for VoIP-related information
Digium - manufacturers of cards (interface to analog phones, POTS lines, T1, etc.) guaranteed to work with Asterisk