Internal electrical connection A Motherboard B Extract air fan tacho (WT) GND (GN) Extract air fan PWM (YE) Supply air fan tacho (WT) GND (GN) Supply air fan PWM (YE) C Extract air Outdoor air Supply air Exhaust air Supply air from the HR cell D LAN MB_A External Modbus A signal MB_B External Modbus B signal +24V +24V voltage (DC) GND Digital and analog ground potential RS_A Local hardware Modbus A signal RS_B Local hardware Modbus B signal NTC External temperature sensor connector D/I1 Digital input 1 D/I2 Digital input 2 11V1 11.1 V operating voltage AN/I Analog input 0-10 VDC RM/I 24V relay input RM/O 24V relay output T Supply air fan P Extract air fan M Damper motor TK Safety switch AHS Post-heating control S/E Fan balance adjustment %RH CO2 Internal humidity and carbon dioxide sensor R1 Post-heating resistor with 90°C and 130°C overheating protection R2 Additional heating resistor with 90°C and 130°C overheating protection