Voltage Comparsion Circuit needed

I want to make such a voltage comparsion circuit which perform the following:-

1) Compare between 24 Volts and less..

2) If the voltage is constant 24 Volts then Logical Low is sent out

3) if the voltage drop below 24 volts it sents out Logical High

Now for this op amp can be used like LM3900 but i am looking for a economical and simple circuit using resistors and capicactor only.

Check out the circuit just below this post "Automotive Ideas" Since you understand the comparitor idea, you should be able to adjust the circuit posted there to 24 volts. As an alternative, do a web search for "comparitor circuits" I am sure you will find exactly what you want.