Sn51dp Datasheet Verified -

                 +5V
                  |
                330Ω
                  |
+5V control ----[Pin1]  SN51DP  [Pin3]---- AC Load (Heater)
GND control ----[Pin2]          [Pin4]---- AC Neutral
                                       |
                                     AC Live

Add a 0.1µF X-class capacitor across AC input lines for noise suppression.

Set DMM to diode mode:

For loads with high L, use internal snubber plus an external 47Ω / 0.1µF across pins 3-4 to prevent dv/dt false triggering. sn51dp datasheet verified

The SN51DP is a dual-port RS-232 transceiver (assumed device class based on typical part numbering). This verification summary confirms key electrical, timing, and packaging specifications from the datasheet and highlights test points for compliance. +5V | 330Ω | +5V control ----[Pin1] SN51DP