In case you have the serial DF1 port of an Allen Bradley PLC, like PLC5, SLC 5/05 1747-L551, SLC 5/03 1747-L533, CompactLogix 1768, CompactLogix 1769, Control Logix 5563, MicroLogix 1400 (1766 MicroLogix ), MicroLogix 1200 (1762 MicroLogix ), MicroLogix 1100 ( 1763 MicroLogix ), MicroLogix 1000 ( 1761 MicroLogix ), or any DF1 device where the DF1 port is already being used and you want to connect another DF1 device to it, usually you would get the Allen Bradley 1747-DPS1 DF1 port splitter but that is being discontinued by Allen Bradley and now your best solution out there is Equustek’s DL4000-DFX which allows three DF1 serial devices to simultaneously communicate with each other, below is the link to DL4000 page .
The DL4000 can be programmed with other firmware versions to perform other protocol conversions, such as;
DL4000-DMX allows DF1 to communicate with MODBUS and can be configured for MODBUS master or MODBUS slave, it also can be configured to connect via RS232, RS422 or RS485.
DL4000-MMX interfaces MODBUS RTU to MODBUS ASCII (Allows Modbus RTU devices to communicate with multiple Modbus ASCII devices), also can be configured to do RS232, RS422 or RS485.
DL4000-DAS Interfaces serial ASCII devices (Scanners/Printers) to AB DF1 protocol.
DL4000-MAS Interfaces ASCII device to MODBUS RTU Slave.
DL4000-PM Provides a DF1 Half Duplex Master Interface to Allen Bradley Power Monitor 3000 then sends the converted data via Modbus to specified Slave RTU devices.