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Connect DC Power to an ACX7100-48L Router


The power supply module (PSM) in an ACX7100-48L router is a hot-removable and hot-insertable field-replaceable unit (FRU). You can remove and replace it without powering off the router or disrupting routing functions.


DC-powered ACX7100-48L routers are intended for installation only in a restricted-access location.


The battery returns of the DC power supply must be connected as an isolated DC return (DC-I).

Before you begin connecting DC power to the router:

  • Ensure that you have taken the necessary precautions to prevent electrostatic discharge (ESD) damage (see Prevention of Electrostatic Discharge Damage).

  • Ensure that you have connected the router chassis to earth ground.


    Before you connect power to the router, a licensed electrician must attach a cable lug to the grounding and power cables that you supply. A cable with an incorrectly attached lug can damage the router (for example, by causing a short circuit).

    To meet safety and electromagnetic interference (EMI) requirements and to ensure proper operation, you must connect the chassis to earth ground before you connect it to power. For installations that require a separate grounding conductor to the chassis, use the protective earthing terminal on the router chassis to connect to the earth ground.

  • Install the PSM in the chassis.

Ensure that you have the following parts and tools available:

  • Phillips (+) screwdriver, number 2 (not provided)

  • Multimeter (not provided)

To connect DC power to an ACX7100-48L router:

  1. Wrap and fasten one end of the ESD grounding strap around your bare wrist, and connect the other end of the strap to the ESD point on the chassis.
  2. Verify that the DC power cables are correctly labeled before making connections to the power supply. In a typical power distribution scheme where the return is connected to chassis ground at the battery plant, you can use a multimeter to verify the resistance of the –48V and RTN DC cables to chassis ground:
    • The cable with very low resistance (indicating a closed circuit) to chassis ground is positive (+). You install this cable on the V+ (return) DC power input terminal.

    • The cable with very high resistance (indicating an open circuit) to chassis ground is negative (–). You install this cable on the V– (input) DC power input terminal.


    You must ensure that power connections maintain the proper polarity. The power source cables might be labeled (+) and (–) to indicate their polarity. There is no standard color coding for DC power cables. The color coding used by the external DC power source at your site determines the color coding for the leads on the power cables that attach to the DC power input terminals on each PSM.

  3. Ensure that the input circuit breaker is open so that the voltage across the DC power source cable leads is 0 V and that the cable leads do not become active while you are connecting DC power.Note

    The V+ terminals are referred to as +RTN, and V– terminals are referred to as –48 V in DC Power Wiring Sequence Warning.

  4. Ensure that the PSMs are fully inserted in the chassis.
  5. Remove the terminal block cover. The terminal block cover is a piece of clear plastic that snaps into place over the terminal block (see Figure 1).
  6. Remove the screws on the terminals by using the screwdriver. Save the screws.Warning

    Ensure that the power cables do not block access to device components or drape where people can trip over them.

  7. Connect each PSM to the power sources. Secure power source cables to the PSMs by screwing the ring lugs attached to the cables to the appropriate terminals by using the screw from the terminals (see Figure 1).

    The ACX7100-48L router is designed to operate with a DC PSM that has a single, non-redundant, feed input. For source redundancy, you must install two DC PSMs in the ACX7100-48L; connect source (A) to one PSM and source (B) to the second PSM. This configuration provides the commonly deployed A/B feed redundancy for the system.


    The connection between each power source and PSM must include a circuit breaker.

    Do not connect two sources to a single PSM because doing so can potentially cause circulating current in feed wires whenever there is any difference in the voltage of the two sources.

    1. Secure the ring lug of the positive (+) DC power source cable to the V+ terminal on the DC PSM.
    2. Secure the ring lug of the negative (–) DC power source cable to the V– terminal on the DC PSM.
    3. Tighten the screws on the PSM terminals until snug using the screwdriver. Do not overtighten—apply between 5 in-lb (0.56 Nm) and 6 in-lb (0.68 Nm) of torque to the screws.
  8. Replace the terminal block cover.
  9. Close the input circuit breaker.Note

    The switch powers on as soon as power is provided to the PSM. There is no power switch on the device.

  10. Verify that the IN and OUT LEDs on the PSM are lit green and are on steadily.
Figure 1: Connect DC Power Cable to an ACX7100-48L Router
Connect DC Power Cable
to an ACX7100-48L Router