What is the difference between RS-232 and TTL 232?

1, Definition and Standards
RS-232, also known as Recommended Standard 232, is a serial data communication standard developed by the Electronic Industries Association (EIA) in the United States. It was originally designed to enable communication between computers and modems, and later gradually expanded to other fields such as industrial automation, medical equipment, consumer electronics, etc. The RS-232 standard defines the electrical characteristics and connection methods of signals, enabling devices produced by different manufacturers to communicate with each other.
TTL 232: The term "TTL 232" here may actually be a misnomer or confusion of concept. In standard terminology, TTL (Transistor Transformer Logic) typically refers to a digital logic integrated circuit standard used for the design and manufacture of logic circuits. TTL 232 "may refer to an interface that uses TTL level signals for communication, or more commonly, an interface that converts TTL levels to RS-232 levels for communication through a TTL to RS-232 converter. To maintain the accuracy of the discussion, we understand "TTL 232" here as the latter, which is the conversion interface between TTL level and RS-232 level.
2, Electrical characteristics
RS-232: RS-232 uses positive and negative voltages to represent logical states, with a typical level range of ± 3V to ± 25V (but in practical use, it is often ± 5V to ± 15V). In the RS-232 standard, voltages greater than+3V represent logic "0", and voltages less than -3V represent logic "1" (note: this is contrary to some descriptions, but we follow the standard's interpretation here). This level design gives RS-232 signals strong anti-interference ability, making them suitable for long-distance transmission.
TTL 232 (TTL to RS-232): TTL levels use low levels (0V to 0.8V) and high levels (2.4V to 5V) to represent logic "0" and logic "1". Due to the low voltage range of TTL levels and their susceptibility to line noise and signal attenuation, TTL signals can usually only be transmitted over short distances. However, by using a TTL to RS-232 converter, TTL levels can be converted to RS-232 levels, enabling long-distance communication.
3, Transmission distance and speed
The transmission distance of RS-232: RS-232 depends on the transmission rate and line noise used. Generally speaking, with low transmission rates and good line quality, the transmission distance of RS-232 can reach about 50 feet (about 15 meters). However, with the increase of transmission rate and line noise, the transmission distance will correspondingly shorten.
TTL 232 (TTL to RS-232): Due to the limitations of TTL level signals, TTL signals can usually only be transmitted within a distance of a few meters to a dozen meters. However, by converting to RS-232 level through a TTL to RS-232 converter, the transmission distance can be significantly extended to tens of meters or even further.
4, Application scenarios
RS-232: Due to its strong anti-interference ability and relatively long transmission distance, RS-232 is widely used in situations that require long-distance communication, such as communication between computers and modems, industrial automation control, and data transmission of medical equipment.
TTL 232 (TTL to RS-232): TTL to RS-232 converters are more commonly used in situations where TTL level signals need to be converted to RS-232 level signals, in order to communicate with more devices based on the RS-232 standard. For example, in embedded system development, developers may need to use a TTL to RS-232 converter to convert the TTL level signal output by the microcontroller into an RS-232 level signal for communication and debugging with computers or other RS-232 devices.