CISCO FXS port configuration allows you to set parameters based on the requirements of the connection. You can alter the default settings and fine-tune the parameters for specific needs. For example, you might need to connect an older phone with a mechanical ringer to a router, and the FXS portâ€™s default ringing frequency does not work for the older phoneâ€™s ringer. You could adjust the ringing frequency parameter to fix that problem. You can set the following configuration parameters for an FXS port:
signal Sets the signaling type for the FXS port. In most cases, the default signaling of loop-start works well. If the connected device is a PBX or a key system, the preferred signaling is ground start. Modern PBXs and key systems do not normally use FXS ports as connections to the network, but older systems might still have these interfaces. When connecting the FXS port to a PBX or key system, you must check the configuration of the voice system and set the FXS port to match the system setting.
cptone Configures the appropriate call-progress tone for the local region. The call-progress tone setting determines the dial tone, busy tone, and ringback tone to the originating party.
description Configures a description for the voice port. You can use the description setting to describe the voice port in show command output. It is almost always useful to provide some information about the usage of a port. The description could specify the type of equipment that is connected to the FXS port.
ring frequency Configures a specific ring frequency (in Hz) for an FXS voice port. You must select the ring frequency that matches the connected equipment. If set incorrectly, the attached telephone might not ring or might buzz. In addition, the ring frequency is usually country dependent, and you should take into account the appropriate ring frequency for your area before you configure this command.
Typically, the ring frequency parameter is an issue only for electromechanical bell ringers. Back in the days of party lines (that is, where multiple residences shared a local loop connection going back to the CO), these mechanical ringers were tuned to ring at different frequencies. However, most modern piezoelectric ringers are unaffected by the ring frequency setting.
ring cadence Configures the ring cadence for an FXS port. The ring cadence defines how ringing voltage is sent to signal a call. The normal ring cadence in North America is 2 seconds of ringing followed by 4 seconds of silence. The United Kingdom uses a double ring of 0.4 seconds separated by 0.2 seconds of silence, followed by 2 seconds of silence. When configured, the cptone setting automatically sets the ring cadence to match that country. You can manually set the ring cadence if you want to override the default country value. You might have to shut down and reactivate the voice port before the configured value takes effect.
disconnect-ack Configures an FXS voice port to remove line power if the equipment on an FXS loop-start trunk disconnects first. This removal of line power is not something the user hears, but instead is a method for electrical devices to signal that one side has ended the call.
busyout Configures the ability to busy out an analog port, perhaps for maintenance purposes.
station id name Provides the station name associated with the voice port. This parameter is passed as a calling name to the remote end if the call is originated from this voice port. Maximum string length is limited to 15.
station id number Provides the station number that is to be used as the calling number associated with the voice port. This parameter is optional and, if provided, will be used as the calling number if the call is originated from this voice port. If not specified, the calling number will be used from a reverse dial-peer search. Maximum string length is 15.