A temperature transmitter is an electronic device used to send a temperature measurement over two wires to the processing unit. The transmitter is responsible for converting the small electrical signal from the temperature sensor into a more readable signal for the processing unit. In most cases, the signal is sent to some sort of programmatic logic controller (PLC) or receiver.
Transmitters are commonly referred to as transducers because of their close proximity in definition and can be used interchangeably.
Transmitters are physically designed to accept and deliver many different types of inputs and outputs. They require a power supply voltage and have different physical shapes depending on your application.