SIMATIC S7-1200, Analog input, SB 1231, 1 AI, +/-10 V DC (12 bit resol.) or 0-20 mA SIMATIC S7-1200 Basic Controller - Flexible thanks to wide variety of communication options If you only have to extend your SIMATIC S7-1200 CPU with a few inputs or outputs, signal boards are a good alternative to signal modules. Signal boards are plugged directly onto the front of the controller (also possible with the CPU 1211C) and are available as digital and analog input, output and hybrid modules. A communications board with an RS 485 interface is also available. Signal boards thus permit subsequent expansion of the configuration without requiring any further space in the control cabinet.