How could a robot respond to pain without being conscious?

robot_pain_response.js

let incoming_electric_signal = get_electric_signal();

// The electric signal could represent the temperature of whatever the robot just touched, say.
// The higher the temperature, the greater the number returned by `get_electric_signal`.

// If some threshold is passed:
if (incoming_electric_signal > 1000) {
  // Detected pain!
  say('OUCH');
}