The Allen-Bradley 1785-L20B is a Programmable Logic Controller (PLC) module. This product is a PLC controller that belongs to the legacy PLC5 product family. The 1785-L20B features a variety of embedded communication ports such as One (1) DH+ (Fixed), One (1) DH+/Remote I/O (Adapter or Scanner) One (1) serial port, configurable for RS-232 and 423 and RS-422A standards. These communications ports support individual configuration and independently functions from each other, They can be used simultaneously to implement the intended functions such as communication to compatible partner devices for data exchanges, communication with visualization devices and interaction with programming workstation. The 1785-L20B’s embedded memory amounts to 16Kwords. This memory is a volatile memory, maintained by a lithium battery with catalog number 1770-XYC. This controller supports implementation of distributed I/O architecture via the DH+ or Remote I/O protocol. It may also be optionally installed with an Ethernet interface module for implementation of distributed I/O system over Ethernet. Up to Twelve (12) remote I/O chassis may be installed with this controller. The 1785-L20B Controller supports installation of a Electronically Erasable Programmable Read Only Memory (EEPROM) as memory backup device. Memory options include 1785-ME16 with 16Kwords, 1785-ME32 with 32Kwords, 1785-ME64 with 64 Kwords and 1785-ME100 with 100Kwords.