BT 8031 –XX series is a CMOS LCI chip is a double sound source with a ROM to play prearranged melodies. The ROM has 127 words and can store upto two melodies with double sound sources. The IC is a three pin type like the popular melody IC UM66. It works between 2-5 volts and ideal voltage is between 2.2V to 3.1V and has very low current consumption ideal for use in battery power supply. Its output cannot drive a speaker directly, so a transistor amplifier is needed.
IC BT8031 series comes in 5 versions each having a pre recorded music. Of these, BT8031-2S is the IC used in Ding-Dong bell. Fig 1 shows the circuit of the Ding-Dong bell using IC 8031-2S