How to Power 4 Devices Over a Single Ethernet Cable: A Guide to PoE Passthrough

Have you ever faced a situation where you needed to install multiple IP cameras or Wi-Fi access points in one location, but only had a single network cable running to that spot?

In the past, this would have required the expensive and time-consuming task of "pulling" three more cables through walls or ceilings. However, with the advancement of IEEE 802.3bt (PoE++) technology, those days are over. In this post, we’re breaking down how to use a 4-Port PoE Extender to maximize your existing infrastructure.

The Problem: The "Single Cable" Bottleneck

Standard networking usually follows a 1-to-1 rule: one cable, one device. If you want to add a VoIP phone and a security camera to a desk that only has one Ethernet drop, you’re usually stuck using a local power outlet or installing a bulky, powered switch.

The Solution: The GBT-4-IW (PoE Passthrough)

The video highlights a specialized solution from PoE Texas: the 4-Port Gigabit PoE Extender. This device acts as a "power splitter" for your Ethernet cable.

How it Works:

1. The Uplink: You take your existing single Ethernet run and plug it into the "Uplink" port of the extender.

2. The Power Source: To make this work, the cable must be powered by a high-output source, specifically an 802.3bt (60-watt) switch or a midspan injector.

3. The Output: The extender "borrows" that 60 watts of power and distributes it across four new ports.

Key Educational Takeaways

1. Distance Extension

Standard Ethernet is limited to 100 meters (328 feet). This device acts as a repeater, allowing you to extend your data and power reach by another 100 meters, effectively doubling your range to 600+ feet from the original source.

2. Understanding PoE Standards (af/at vs. bt)

To use an extender like this, you need to understand the "Power Budget":

• Input (802.3bt): Provides up to 60W of power to the extender.

• Output (802.3af/at): The extender can then provide power to four "af" devices (like basic IP phones) or two "at" devices (like high-end PTZ cameras or Wi-Fi 6 Access Points).

3. No Local Power Required

The most "educational" aspect of this technology is that it is self-powered. You do not need to find a wall outlet to plug the switch into. It draws its operating power directly from the Ethernet cable itself.

Step-by-Step Installation Guide

Step 1: Check your Power Source Ensure your main network switch supports IEEE 802.3bt. If it doesn't, you can use a 60-watt PoE injector (like the BT-1-55v60w) between your switch and the long cable run.

Step 2: Connect the Uplink Plug the long-run cable into the designated Uplink port on the GBT-4-IW. You should see the LED lights flicker, indicating the device has successfully "woken up" using the incoming PoE.

Step 3: Connect your Devices Plug in your cameras, access points, or VoIP phones. The extender will automatically negotiate the power needs for each device.

Step 4: Optional VLAN Configuration Many of these extenders come with a VLAN switch. If you are installing security cameras, toggling this can help isolate camera traffic from the rest of your network for better security and performance.

Ideal Use Cases

• Parking Lots: One cable run to a pole can now power four different security cameras.

• Office Retrofits: Turn one wall jack into a hub for a computer, a VoIP phone, and a wireless AP.

• Warehouses: Extend Wi-Fi coverage across large floor plans without hiring an electrician to install new outlets.

Final Thoughts

Technology like the IEEE 802.3bt extender proves that you don't always need more wires—you just need to make your existing wires work harder. By leveraging PoE passthrough, you save on labor, materials, and time.