int incomingByte = 0;	// for incoming serial data
int transistorPin = 9;

void setup() {
	Serial.begin(9600);	// opens serial port, sets data rate to 9600 bps
        pinMode(transistorPin, OUTPUT);
}

void loop() {

	// send data only when you receive data:
	if (Serial.available() > 0) {
		// read the incoming byte:
		incomingByte = Serial.read();
                
                if (incomingByte == 1) {
                  digitalWrite(transistorPin, HIGH);
                } else {digitalWrite(transistorPin, LOW); }
	}
}