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.
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.