Product Description:

The CU1521-0010 is an EtherCAT junction produced by Beckhoff and assigned to the CU EtherCAT Junctions series. This DIN-rail module combines copper and fiber interfaces so field devices can be attached to an existing EtherCAT line or branched into star and tree topologies. In industrial automation networks, the junction routes frames at hardware speed, allowing controllers to extend segment reach without adding active switches.

The copper section contains two Ethernet ports that communicate at 10BASE-T/100BASE-TX rates. By adhering to IEEE 802.3u auto-negotiation, the junction and the attached device automatically agree on the fastest mutual speed, reducing manual setup errors. Duplex mode can be selected as half or full duplex, so the link can either share transmission time or transmit and receive simultaneously, which affects throughput and collision handling. Because the unit processes Ethernet traffic in store-and-forward mode while forwarding EtherCAT telegrams in cut-through mode, latency is minimized for real-time control while faulty Ethernet frames are still dropped. During operation, the electronics draw only 80 mA, a value that simplifies sizing of the control cabinet power bus.

The fiber branch introduces a single SC duplex connector working with 100BASE-FX signaling over single-mode cable. A nominal supply of 24 VDC powers both the optical transmitter and the internal logic without external converters. The laser operates at 1310 nm, matching common single-mode transceivers used on the plant floor. Segment reach depends on the medium: copper segments may extend to 100 m, while the optical path can bridge up to 20 km between nodes, enabling long-distance machine islands to share one controller. An IP20 housing protects the circuitry from incidental contact and settled dust, and the current and voltage limits keep thermal load low so the junction can reside next to PLCs and drives in compact enclosures.