Problem 1 Choose title 1 st XML 2 nd electronic spider 3 rd infrared remote home control Waste time

Problem 2 Write Program Added Delay subroutine Added Table Loop Delay execution time Not necessary

Test Result Input (dual-tone signal)Output (89C51 port1 LEDs) pin8 to pin off 1-on

Problem 3 LEDs unstable Use resistor connect 5V Pulled the LEDs HIGH LEDs become stable

Problem 4 Remove Reset button Cannot receive input signal properly Added the Reset button in 89C51 pin 9 89C51 receive signal before pressed Reset button

Problem 5 Test success in the breadboard Tried to connect to the board Telephone’s current breaks down the 89C51 Added a relay counter Hold the input current

Problem 6 MT8870 does not auto hook off on telephone Connect to 4040 & RY6WFZ-K relay to MT8870 Ringing value at 2 to power 12 Can auto hook off the phone

Problem 7 Voltage of ringing signal between +1.4V to –1.4V Unstable & Not enough power Connect 4040 with amplifier & transistor Pulled HIGH the voltage Rectified the current

Problem 8 Dual tone receive signals– Full wave rectified 4040 counter only accept – Half wave rectified Added a diode to transfer Signal become half wave rectified

Problem 9 Signal’s current too high 4040 Counter break down Change the 4040 counter Added a relay to prevent

Test Result Phone in  Phone  4040 counter auto hook off  Key pressed  Dual tone  MT8870  Binary code  89C51  LEDs Display the result

MT8870 & 89C51 scematic

MT8870 & 89C51 breadboard

Relay & 4040 counter schematic

4040 counter & relay breadboard

Power supply schematic

Power supply board