Patent ID: 6982641

Claim:
A simplified control circuit for an intrusion detection device, comprising: an intrusion detection alarm comprising a normally closed terminal, normally open terminal, and common terminal; a ground terminal connected to the common terminal; a direct current supply having a first voltage sufficient to power the control circuit in a standby and an active state, having positive and negative terminals; a power terminal connected by a first return line to the positive terminal; a first resistor, having a first resistance, placed between the normally open terminal and the normally closed terminal; a second return line connected from the normally open terminal to the negative terminal; a second resistor, having a second resistance, connected in the second return line, wherein current passes through the first and second resistor when the intrusion detection alarm comprises the standby state; and, a zener diode, having a peak reverse voltage, and in series with an LED that are both placed in parallel with the second resistor wherein a voltage drop across the second resistor comprises insufficient voltage to reach the peak reverse voltage in the standby state and wherein the active state removes the first resistor from the circuit, reduces the voltage drop across the intrusion detection alarm, and increases the voltage drop across the second resistor to result in a voltage over the peak reverse voltage across the zener diode that allows it to conduct and illuminate the LED.