The EL1804 digital input terminal acquires the binary 24 V control signals from the process level and transmits them, in an electrically isolated form, to the higher-level automation unit. The EtherCAT Terminal contains four channels whose signal state is indicated by LEDs. The power contacts are connected through. With the EL1804, the reference ground for all inputs is the 0 V power contact.

Special features:

• input specification type 1/3
• no bouncing due to mechanical switches thanks to 3 ms input filter
• +24 V and 0 V sensor supply connections
• tool-free connection by direct plug-in technique for solid wire conductors
• increased packing density with 16 connection points in the housing of a 12 mm terminal block

https://www.beckhoff.com/vi-vn/products/i-o/ethercat-terminals/el1xxx-digital-input/el1804.html