miltizem

I am working on a project .. telephony one .. i am using a LM567 but i didn't get yet what does it d exactly .. the thing is that i have to program its function on LabVIEW even...
I know it detects a frequency .. but what for ? Also , what's its output ?
So plz can someone help me with that ... it's very very urgent .. thanks in advance

crutschow

When the LM567 detects a particular frequency it turns on a output transistor to ground (to get a digital signal you add a pullup resistor to the output). The device detection frequency and bandwidth (the range of frequencies it will detect) can be controlled by external resistors and capacitors. 7 of them can be used to decode the touch-tone signals from a telephone to give outputs 0 through 9 plus the * and # characters (see the National Semiconductor LM567 data sheet, pg. 5).

miltizem

one question .. doesn't it give a frequency as an output .. ok it turns a transistor to the ground .. but what is the signal on the output ? is it logical 0 or 1 ? o or 5v ?

crutschow

It does not give a frequency output. It gives a digital output. 0V when it detects a frequency. A high ouput voltage when no signal is present.
The high output voltage depends upon the voltage connected to the pullup resistor, up to 5V. For example, it could be 3V if you wanted a 3V logic signal.