The Siemens 6GK1 551-2AA00 is a CP 5512 communications processor, a 32-bit Cardbus PC card designed for connecting programming devices (PGs) or notebooks to Siemens PROFIBUS or MPI networks. This module allows users to interface with their industrial control systems for programming, monitoring, and diagnostics. 
Key characteristics: 

• Manufacturer: Siemens
• Product Family: SIMATIC NET
• Part Number: 6GK1 551-2AA00
• Type: Communications Processor (CP) 5512
• Interface: PC Card (Cardbus, 32-bit)
• Functionality: Connects a PC or notebook to a PROFIBUS DP or MPI network.

Purpose:
The CP 5512 card enables industrial communication for tasks such as: 

• Programming: Uploading or downloading programs to Siemens PLCs.
• Monitoring: Real-time observation of network traffic.
• Diagnostics: Analyzing network performance and troubleshooting issues.

Status:
The CP 5512 (6GK1 551-2AA00) has been type discontinued by Siemens since October 1, 2015. Its functional successor is the USB 2.0 module CP 5711.