     Serial.print(gate_input);
     Serial.write(")");
 
-    Serial.write("\r\nDrain input: ");
+    Serial.write("\r\nDrain voltage: ");
     if (power15_mv > 5000) {
         print_mv(drain_mv);
         Serial.write(" (");

    // Configure pins.
    // D2 - gate output
    // A0 - gate input
    // A1 - drain input with divisor 1:4.3
    // A2 - +5V input with divisor 1:2
    // A3 - +15V input with divisor 1:4.3
    //
    pinMode(gate_output_pin, OUTPUT);
    pinMode(A0, INPUT);
    pinMode(A1, INPUT);
    pinMode(A2, INPUT);
    pinMode(A3, INPUT);

    // Configure timer 3 prescale factor as 1:1.
    // Set bits CS32,CS31,CS30 to 0b001.

#define DRAIN_MULT      (((33 + 10) / 10.0) * CALIBRATE_DRAIN)      // resistors 33k and 10k
#define POWER5_MULT     (((10 + 10) / 10.0) * CALIBRATE_POWER5)     // resistors 10k and 10k
#define POWER15_MULT    (((33 + 10) / 10.0) * CALIBRATE_POWER15)    // resistors 33k and 10k
#define DR_CURRENT_MULT (100000.0 / 220 / 51)                       // resistors 51 and 220

/*
 * Read a character from the serial port.
