# Using an alternative power supply

You can use a power supply other than the NMS power supply. This power supply must provide:

- DC voltage to provide talk battery power to the station telephones.

- AC and DC ring voltage, if your application involves ringing station telephones. The AC voltage provides the ringing power. The DC voltage provides loop current that signals the CX board when the telephone goes on or off hook.

This topic specifies the power supply requirements for different boards and describes how to connect an alternative power supply.

## Power supply requirements

The tables in this topic specify power supply requirements for different boards, cable lengths, and resistive loads.

Cables between the power supply and the board must be rated for 2 A per board or greater. Twisted pair cabling is recommended for noise reduction.

Warning: | In the worst case, the ring voltage must not exceed 92 V AC, and the DC voltage must not exceed 52 V DC.

An AG 2000 power supply can be substituted for the rack mount supply for one CX 2000 board. The cable supplied with the AG 2000 power supply will mate with the connector on the board.

### CX 2000 power supply requirements

For CX 2000 boards, AC voltage is required only if you are enabling ringing of station telephones.

Length of 24 AWG cable | Max resistive load | Recommended output
--- | --- | ---
Talk battery | Ring voltage(only if ringing required)
0 to 2000 feet | 600 Ohms | -24 V DC | 55 to 89 V AC and -24 V DC
> 2000 feet | Not supported.

The ring signal circuitry in the power supply must be equivalent to the following illustration:

Ring signal schematic (for CX 2000 power supply)

## Connecting an alternative power supply

Connect the power supply to the TELCO POWER connector on the end bracket of the board. The following illustration shows the power connector pinouts for the CX 2000 board:

Power connector pinouts

The mating connector is Molex 43025-1000 with Molex 43030-0001 or Molex 43030-007 pins.

If only one DC output is available, it must be connected to both the high battery input and the low battery input.