and then, i look through the datasheet of the ZN414 IC. it says that the frequency range (input) is only 0.15 to 3 MHz. so i measured the input and output of the IFT (input to the ZN414 IC) and i found that the frequency is about 580Hz (the frequency of the 555 timer at the transmitter). so why is it so???? so it goes back to my first question, what is the frequency of the oscillator circuit? and can all of these factors affect my output of the NE567. Now, i still cant get a output sufficient to turn on the relay. the output from the NE567 i got is about 3mV peak and i have no idea how can it be used to trigger the relay. Any idea? please let me know why.