The Siemens S7-200 SMART Digital I/O SB DT04 with 6ES7288-5DT04-0AA0 is S7-200 SMART PLC series. It is designed to be a small, low-cost expansion module that plugs directly into the CPU to add I/O points.
The Siemens 6ES7288-5DT04-0AA0 is an active product. The S7-200 SMART series is a popular and current product line from Siemens. Designed to be a simple plug-and-play addition to standard type S7-200 SMART CPU modules. It is not compatible with the compact CR series CPUs.