Timers and Timing Configuration Parameters

Timers and Timing Configuration Parameters

You can set a number of timers and timing parameters for fine-tuning the voice port. Following are voice port configuration parameters that you can set:

• timeouts initial Configures the initial digit timeout value in seconds. This value controls how long the dial tone is presented before the first digit is expected. This timer typically does not need to be changed from its default of 10 seconds.

• timeouts interdigit Configures the number of seconds for which the system will wait for the caller to input a subsequent digit of the dialed digits after the caller has input the initial digit. If the digits are coming from an automated device and the dial plan is a variable-length dial plan, you can shorten this timer so that the call proceeds without having to wait the full default of 10 seconds for the interdigit timer to expire.

• timeouts ringing Configures the length of time that a caller can continue ringing a telephone when there is no answer. You can configure this setting to be less than the default of 180 seconds so that you do not tie up the voice port when it is evident that the call is not going to be answered.

• timing digit Configures the DTMF digit-signal duration for a specified voice port. You can use this setting to fine-tune a connection to a device that might have trouble recognizing dialed digits. If a user or device dials too quickly, the digit might not be recognized. By changing the timing on the digit timer, you can provide for a shorter or longer DTMF duration.

• timing interdigit Configures the DTMF interdigit duration for a specified voice port. You can change this setting to accommodate faster or slower dialing characteristics.

• timing hookflash-in and hookflash-out Configures the maximum duration (in milliseconds) of a hookflash indication. Hookflash is an indication by a caller that the caller wishes to do something specific with the call, such as transfer the call or place the call on hold.

  For hookflash-in, if the hookflash lasts longer than the specified limit, the FXS interface processes the indication as on hook. If you set the value too low, the hookflash might be interpreted as a hang up; if you set the value too high, the handset has to be left hung up for a longer period to clear the call.

  For hookflash-out, the setting specifies the duration (in milliseconds) of the hookflash indication that the gateway generates outbound. You can configure this to match the requirements of the connected device.

The installation in Figure 3-11 serves as a solution in a home for the elderly, where users might need more time to dial digits than in other residences. Also, there is a requirement to allow the telephone to ring, unanswered, for only one minute. Figure 3-11 shows an analog phone connecting into FXS port 1/0/0 on a voice-enabled router.

The FXS port's configuration, as shown in Example 3-4, enables several timing parameters for this voice port. The initial timeout is lengthened to 15 seconds, the interdigit timeout is lengthened to 15 seconds, the ringing timeout is set to 60 seconds, and the hookflash-in timer is set to 500 ms.