The intelligent FM 350-1 counter module has one counting channel for up and down counting, and is an excellent choice for universal high-frequency counting tasks up to 500 kHz.
It also features measuring functions for speed, frequency and period length. In distributed configurations with S7-400 or WinAC RTX, the FM 350-1 supports isochrone mode.

The FM 350-2 counter module, by contrast, is an 8-channel counter module for universal counting and measuring tasks up to 20 kHz.
It can be used in the SIMATIC S7-300 and in the ET 200M (with S7-300/S7-400 as master).