- Many phones today come with the answering machine already built in. When a caller leaves a message, the voice becomes a stream of bytes. Inside the answering machine, there is a microcontroller that digitizes the message the caller left. An analog-to-digital converter makes the voice digital. The digital answering machine uses solid state memory storage. The digitalized message is stored in low-power RAM (Random Access Memory).
- When a message is left on an answering machine and digitized into bytes of data, it is stored at a specific address in RAM. When the owner plays back his messages, the microcontroller reads the bytes from RAM and sends them through a digital-to-analog converter. Then the owner of the answering machine hears the caller's voice and message through the speakers. When the owner deletes a message, other messages are still available and will be played in order. This is because RAM is a high-speed memory device. The microcontroller moves up the other messages into freed-up space when a previous message is deleted.
- Kazuo Hashimoto invented the digital answering machine in 1983. It was called the Automatic Digital Telephone Answering Device. An answering machine is also commonly referred to as an answerphone or telephone answering device (TAD). The owner records a greeting that is played when the answering machine answers a phone call, and the answering machine can be set to answer after a certain number of rings. Another common feature of digital answering machines is that the owner can remotely check his messages by calling home and keying in a code.
