The MT8870 DTMF Audio/Speech Decoding Telephone Module is commonly used to control robots with a mobile phone, it is also used in different kinds of home automation projects where mobile dial pad input is required.
The 2SC828 is an NPN, Silicon-based AF Amplifier Transistor that is mainly used in AF based audio equipment for amplification and switching. It has a Collector-Emitter Voltage of 25 Vdc with a Collector-Base voltage of 25 Vdc.
The DAC0808LCN is an 8-bit monolithic digital-to-analog converter (DAC), It will interface directly with popular TTL, DTL or CMOS logic levels, and is a direct replacement for the MC1508/MC1408. For higher speed applications.
The TIP31C is a base island technology NPN power transistor in TO-220 plastic package with better performances than the industry standard TIP31C that make this device suitable for audio, power linear and switching applications. The PNP type is TIP32C.