# Configuring the internal ringer unit

A CX 2000C-32-R board includes an internal ringer unit: circuitry that can ring a limited number of telephones based on chassis power. This board can ring 12 telephones with a ringer equivalence of 1.0 at one time. Cable length is limited to 3000 feet.

The internal ringer unit circuitry is located on the CX 2000C-32-R rear I/O transition board.

If your board contains an internal ringer unit, you must select the ringing frequency. On the rear I/O transition board, switches 3 and 4 on DIP switch S1 control the ringing frequency. Set the switches as shown in the following table:

For a ringing frequency setting of... | Set S1 switches 3 and 4 (rear I/O transition board) to the following settings...
--- | ---
Switch 3 | Switch 4
20 Hz (default) | OFF | OFF
16.7 Hz | OFF | ON
25 Hz | ON | OFF
50 Hz | ON | ON

On the rear I/O transition board, switches 1 and 2 on DIP switch S1 control other ringer configuration options. These settings are preset.

DIP switch S1 (rear I/O transition board) | Description
--- | ---
1 | Ringer enabled (default). Set to ON if the internal ringer unit is present on the board.
2 | Battery return to ground. Must always be set to ON. Do not change this setting.

Jumper pin block JP1 on the rear I/O transition board specifies the source of the ring voltage:

JP1 setting (rear I/O transition board) | Description
--- | ---
Jumper on pins 1 and 2 | Ring voltage comes from the internal ringer unit circuitry.
Jumper on pins 2 and 3 | Ring voltage comes from the external power connector (J8).

Jumper pin block JP4 on the main board specifies whether ring voltage is coming from the rear I/O transition board or from the CompactPCI telecom power bus. For more information, refer to Using the NMS rack mount power supply chassis.

JP4 setting (main board) | Description
--- | ---
Jumper on pins 1 and 2 | External ring voltage from rear transition board (default).
Jumper on pins 2 and 3 | Ringing voltage from CompactPCI telecom power bus.