The simulation of alarm circuit of Syma X5 quadrocopter in RC Groups forum. See http://www.rcgroups.com/forums/showthread.php?t=2590612
There are comparison of effects when different resistor values are used. At top are original circuit. At bottom - same circuit with optimized resistor values which have less current draw and no input resistor heating. Resistor from Vcc to input should have large resistance: 100...680 kOm. Resistor between input and transistor base should be 2.2...6.8 kOm.
Lamp represents the 3V active buzzer (at now there is no buzzer element available).
