Yes, we’ve had some hands-on experience with the Siemens OP121, and it’s been quite impressive. In comparison to replacing the PE-11, the OP121 offers several notable improvements. Firstly, its enhanced processing power allows for quicker response times and better overall performance. Additionally, the OP121 boasts improved compatibility with modern fire alarm systems, providing seamless integration and enhanced functionality. Overall, upgrading to the OP121 from the PE-11 is a wise choice for those looking to optimize their fire alarm system’s efficiency and reliability.