Hands free
The presence of a hands-free function in the FM transmitter.
The speakerphone implies the presence of Bluetooth (see the relevant paragraph) and allows you to conduct conversations by broadcasting the voice of the interlocutor through the car's speaker system. This is the best option for talking on the phone while driving — the phone does not need to be held in your hand, and the audibility is better than from the device's own speaker.
At the same time, it is worth noting that the presence of Bluetooth in the FM transmitter does not mean the presence of this function, it requires the presence of a microphone. However, there are also
transmitters without a microphone. In one case, in order not to make the conversation public when there are other people in the salon; in the second case, for models without Bluetooth at all.
Voltage indication
Transmitters that allow you to
display the voltage of the on-board network, so as not to accidentally completely discharge the battery. Or to indicate the corresponding parameter for older cars that do not have such a function.
Card reader
A slot that allows you to install memory cards in the FM transmitter and play music from them. Most often, card readers are made for SD or microSD form factor cards; however, both varieties have several variations (SDHC, SDXC), so before using such a transmitter, it's ok to clarify which varieties the
card reader is compatible with.
Media support
File formats supported by the FM transmitter.
Almost all models support the MP3 format, which is the most common modern digital audio format. Some devices are also capable of working with WMA — this is also one of the main formats, but for a number of reasons it is used much less often. And even less common is compatibility with WAV — this format provides higher sound quality, but with FM broadcasting this advantage is lost, and the files themselves take up noticeably more space than MP3 and WMA.
Charging port
The transmitter has a specialized
USB port for charging smartphones, tablets and other external devices.
Note that you can also charge external devices from conventional USB connectors; however, specialized ports provide higher power output, which can significantly reduce charging time. It is also worth mentioning that the specific purpose of such a connector can be different: in some models it works only as a power source, in others it can also be used to connect USB drives. Many FM transmitters have two USB ports — regular and charging; this allows you to simultaneously charge an external gadget and listen to music from a USB flash drive. And in modern devices, the old USB A form factor is supplemented by a modern
USB-C port.
Fast charge
The quick charge function, as the name suggests, allows you to significantly reduce the time spent on the procedure. This is achieved through increased current and/or voltage, as well as "smart" process control (at each stage, the current and voltage correspond to the optimal parameters). At the same time, the rechargeable gadget must also have a similar fast charging technology.
