Figure 1. HMT130 component board. Figure 1 shows the main parts of the HMT130 component board, including the wiring connectors. 1 Optional LCD display 2 Indicator LEDs 3 Adjustment buttons 4 Service port 5 RS-485 bus termination switch 6 Relay terminals 7 RS-485 bus 8 Analog outputs 9 Power supply connectors