Bayer HealthCare RapidPoint 400 Series Service Manual page 91

Signal HEAT24V_EN controls power to the heaters and is enabled by a
latched bit on IC U38 on the RTP data bus. LEDs CR10 to CR13 indicate
which of the four power supply voltages (VCC, +12 V, -12 V, and +24 V) is
present.
Rev. C Electronic System Overview 91