Question

1. Before digital cell phones, land-line telephones used a system called DTMF – Dual-Tone Multi-Function “touch-tones” to send numeric entry over the phone (it is still used today when the automated caller says “Press 2 to be placed on our do-not-call” list.
   1. Design an analog circuit that will trigger a light to turn on when the number 5 is pressed. It shall not turn on if any other keypad button is pressed.