With the progress of digital technique, processing of a large capacity of data is enabled and digital recording is adopted for recording various signals. In the field of sound signal recording, compact disks and the like which adopt digital recording have become widespread. An optical disc recorder records data on an optical disc, which serves as a recording medium. Many compact discs contain songs, musical compositions and other audio programs in digital form. There are many types of compact disk players. Some are contained in large audio systems with amplifiers and speakers. Other compact disk players are portable and connected to headphones. Most compact disks are prerecorded at a recording studio. A CD-DA family compact disc-recordable (CD-R) drive is one type of optical disc recorder that is widely used. A CD-R is a write-once optical disc on which data is written only once. The recorded data cannot be physically deleted. A laser beam is irradiated against the optical disc from an optical head of the CD-R drive. The heat of the laser beam melts a dye and forms recording pits on a recording layer of the optical disc. An MD (mini disk) is a magneto-optical disk on which information obtained by converting music into digital data. Digital information, such as music information, is previously recorded on an optical disk or in a state of a so-called free magneto-optical disk on which a user can record desired digital information using an MD recorder. Data is recorded on the disc by changing the reflecting rate of the recording layer. Optical disks can also be played on the CD drive of many computer systems. Since the audio programs on the CD are in digital form it is possible to copy those digital programs and save them as digital audio files in the memory of the computer system. An optical disc recorder includes a buffer memory and an encoder. The buffer memory temporarily stores data provided from an external device, such as a personal computer. The encoder reads the data from the buffer memory and encodes the read data to record the data on the optical disc.

In recent years, digital audio recorders have been developed in which the audio information is stored as digital data in a solid state memory. Digital audio recorders generally employ nonvolatile semiconductor memory, such as flash memory, as a recording medium. A single memory device may store several recorded messages, so address information indicating where each message begins and ends is also stored. In a semiconductor memory device, the time required for storing and retrieving information generally is independent of the physical location of the information within the memory device. Semiconductor memory devices typically store information in a large array of cells. A group of cells are electrically connected together by a bit line, or data line. An electrical signal is used to program a cell or cells. Semiconductor memory can broadly be categorized into two major families that are characterized by whether or not their data is retained when power to the memory is removed. Volatile memory, which loses its data when the power is removed, is commonly referred as random access memory (RAM). Non-volatile memory retains its data when the power to the device is removed. There are various types of nonvolatile memories including e.g., read only memories (ROMs), erasable programmable read only memories (EPROMs), and electrically erasable programmable read only memories (EEPROMs), and flash memory. Flash memory is often used where regular access to the data stored in the memory device is desired, but where such data is seldom changed. Computer applications use flash memory to store BIOS firmware. Peripheral devices such as printers store fonts and forms on flash memory. Digital cellular and wireless applications consume large quantities of flash memory and are continually pushing for lower voltages and higher densities. Portable applications such as digital cameras, audio recorders, personal digital assistants and test equipment also use flash memory as a medium to store data. A memory card is a card-type semiconductor device mounting a semiconductor chip in which a memory LSI for data storage or program storage is formed, and is connected to various kinds of electronic equipments such as a digital camera, a handheld PC, an audio recorder and the like when in use. A memory card using a flash memory can be freely attached to an apparatus and detached therefrom.

Digital audio recorders are used as voice memo recorders, and as voice message recorders in portable telephone sets. Digital audio recorders may record analog values representing the instantaneous amplitude of the sound reaching the unit's microphone or the microphone output may be digitized and stored as binary values. An audio recorder that uses a memory card as a record medium typically employs a data compressing method which allows data to be restored in a relatively high quality for recording/reproducing. Digital compression/decompression circuits may be employed to increase storage capacity for a fixed memory size. Often these recorders employ sound responsive switches to reduce the battery drain when there are no sounds to be recorded. An audio signal compressed with a variety of compression formats, represented by MP3 (MPEG layer 3), is also often replayed with computers. Such audio signal is also frequently replayed with a portable-dedicated player that has a semiconductor memory of which capacity is relatively small. Encryption techniques can be implemented to protect the copyright of music titles recorded and reproduced with this audio recorder. The audio recorder can be designed to determine, via an encryption technique, whether a memory card is invalid and thus prohibited from being used with the recorder. Digital audio recorders incorporate file-based content transfer capability. This capability has been performed, for example, by USB connectivity or by compatibility with a digital file removable storage media such as memory atick available also on the PC, along with many other transfer mechanisms. In recent years, digital voice recording capabilities have been expanded from dedicated voice recorders to other consumer electronic categories  which include digital music players with MP3, cellular phones or personal digital assistants devices with built in or external microphone input, and digital imaging devices capable of image, text, or video as well as audio recording. All of these and other devices may be considered digital audio recording devices for purpose of this document as long as they can be adapted to download audio files recorded on the device to a computer.