Cassette tape adaptor
The cassette adapter allows one to play music through sound systems with a tape player without the need for an auxiliary input.
A cassette tape adapter is a device that allows the use of portable audio players in older cassette decks. This is useful for cars, which often lack inputs for portable devices. Originally designed to connect portable CD players to car stereos that only had cassette players, the cassette tape adapter has become popular with portable media players even on cars that have CD players built in.
A typical cassette adapter uses a single-sided writing tape head (similar to the recording head on a traditional tape deck) connected to a stereo minijack connector with a cord. The cord is connected to the device's output (or headphones) port and the electrical signal is converted into a magnetic signal by the head. This magnetic signal is then received by the tape deck's reading head, converted back into an electrical signal, and amplified by the sound system. Because most cassette adapters use a single-sided head, they only work in one direction. There are, however, some cassette adapters that have double-sided heads that work in either direction.
A common alternative to cassette adapters is FM transmitters. These devices often require external power and convert the device's electrical signal into radio waves which are then transmitted over an unused FM frequency to a nearby FM tuner. The cassette adapter is usually considered superior as it is much less prone to interference, though some car radios without cassette players support receiving frequencies lower than the typical FM broadcasting range for the US (i.e. some radios receive frequencies below 88.1, and there are some FM transmitters that transmit below 88.1).
A cassette adapter could also be used with other audio equipment, such as a microphone, handheld game console, or laptop computer. It can also be used in a home tape deck to play sound from any equipment, such as a personal computer, when computer speakers are in short supply.
A cassette adapter is shaped like a cassette tape. However, instead of having reels of tape inside, it has a transmitting head where the tape is normally read by the reading head. This transmitting head is connected to the input cord, which connects the head to the portable device. A cassette adapter must also include a mechanism that simulates tape movement. Modern cassette players monitor tape movement to detect when the tape ends. This is done using a rolling wheel that rides against the tape. To simulate tape movement, a system of gears or a drive belt connects the tape player's drive motor (via the take-up spindle) to a wheel inside the adapter. This wheel rides against the detection wheel to simulate tape movement. Because the wheel never stops spinning, the deck never senses an end-of-tape and never tries to reverse the tape.