Digi 500157 Passive PoE Injector for MX-Series Routers

The Digi 500157 passive PoE injector solves the placement problem for MX-series routers: the best cellular signal is rarely next to a power outlet. The injector sits at the convenient end of the Ethernet run—an equipment closet, UPS shelf, or desk—and combines DC power with network data onto the single cable feeding the router. At the far end, the MX-series device receives both, mounting wherever the site survey says it should. Passive PoE differs from standards-based 802.3af/at/bt in that there is no negotiation: the injector applies power directly, and the powered device must be designed for it. That is exactly the case here—the 500157 is the injector specified for Digi's MX-series family, so voltage and pinout match the routers it feeds. The corollary discipline: do not plug non-PoE or standards-PoE equipment into a passive injector's output, and label the run accordingly. Operationally, injector-fed deployments centralize power where it can be protected. Landing the injector on a UPS keeps the remote router alive through outages—the defining requirement for failover connectivity, which only earns its keep when primary power and circuits are misbehaving. At about 0.1 lb, the injector adds nothing to an install kit, and stocking one or two spares insures sites against the most commonly failed component class in distributed deployments. Verify your specific MX-series model and follow Digi's cabling guidance for maximum run length.