Siemens digital input module sm 1221 series siemens 6es7221 1bh32 0xb0 the siemens 6es7221 1bh32 0xb0 is a sm 1221 digital input signal module that converts the level of the external digital signals from the process into the internal signal level of the s7 1200 the signals can be mixed as desired and users can then adapt their controllers exactly to the relevant task this signal module is supplied with 16 input channels siemens 6es7221 1bh32 0xb0 sm 1221 digital input module