Private-line automatic ringdown (PLAR) circuits have statically configured endpoints and do not require that the user dial in order to connect calls. The connection plar command provides a mechanism to create a switched VoIP call without digit dialing. PLAR connections are often referred to as a bat-phone type of application. This is when a phone (or DS0) goes off-hook and a remote phone rings (or remote DS0 goes off-hook) without digits being dialed. This is a useful tool for customer requirements such as:
The provision of an Off-Premises eXtension (OPX) from a private branch exchange (PBX).
Connection PLAR allows remote users on Foreign Exchange Station (FXS) ports to look to a central PBX like physical extensions.
The provision of dial-tone from a remote PBX.
Many customers want to offer toll-bypass VoIP services without having the routers provide dial-tone or change their existing dial plan. This allows stations at remote sites to look like they are physically connected stations to a PBX.