Manual

16
VI. Telephone Connections
Introduction to SIP
SIP (Session Initialization Protocol) is the standard used by EarShot IFB to talk to virtual phone lines. These
lines must be created in some way externally before they are “applied” to EarShot IFB. “Applying” SIP lines
involves configuring the mainframe with certain information about the lines and the location of the server that
delivers them. Then the mainframe can be allowed to register with the SIP server and automatically handle
all of the interface with the virtual line.
The SIP line can be delivered from several sources:
1 A commercial telephony provider that delivers SIP-based lines over a public or private IP
network.
2 A PBX that delivers telephony to extensions via SIP (in this case the EarShot IFB mainframe is
treated like a PBX extension).
3 A hardware gateway device designed to bridge legacy telephone services to SIP. These
devices interface to the outside worlds via analog POTS/PSTN cables, T1/E1 circuits, or ISDN.
They interface to EarShot IFB via IP over Ethernet.
The setup and interface are identical for options 1 & 2 and similar for option 3.
The first step in setting up a SIP-based phone line is establishing an account with some kind of SIP based
provider or PBX. This process can’t be described here, but the result of this process is that you will have access
to certain credentials for that account. These typically consist of:
• Server Domain - The IP address or URL of the server to which you are being registered.
• Username - The name that EarShot IFB will use when logging into the service.
• Password - The password associated with your account for security purposes.
In addition, several SIP providers require an Authorization Username (Auth Username), which is often
defaulted to be the same as the username but sometimes is required to be different.
SIP is a complex protocol, and is based on Internet standards documents called RFCs. These documents are
often subject to interpretation, and some PBXs, gateways, or telephony providers may have some obscure
SIP settings requirements to work best with EarShot IFB. However, most should work with just the credentials
noted above.
Once EarShot IFB is set up to work with a PBX or Internet Telephony Provider, it will automatically register with
the correct server and maintain a connection to the server indefinitely. This way, the provider or PBX can notify
EarShot IFB of incoming calls to its phone number.
With hardware gateways, the process is reversed. EarShot IFB will actually emulate a SIP server to the
gateway device. The credentials will be entered into the gateway device. EarShot IFB will only need to know
the address of the gateway device.