The following inputs are reserves for future expansions:
• Auxiliary heater (D_ZHA, 4.31/1.04)
• Input stage for switching signal (S_, 2.12/1.04)
• Input stage for switching signal (S_, 4.34/1.04)
• Input stage for switching signal (S_, 4.39/1.04)
• Input stage for switching signal (S_, 4.25/1.04)
