Is RS232 5V or 3.3V?

We need to understand the history and development of the RS232 standard. The RS232 standard was initially introduced by the Electronics Industry Alliance (EIA) in the 1960s, aiming to provide a reliable transmission method for serial communication between computers and other electronic devices. At the beginning of the introduction of this standard, the voltage level of 5V was widely adopted, partly because electronic components at that time mostly used 5V as the standard operating voltage, and partly because 5V voltage could provide sufficient swing to ensure long-distance signal transmission and anti-interference.
However, with the development of electronic technology, especially the advancement of integrated circuit manufacturing processes, 3.3V logic levels have begun to become popular in electronic devices. This is mainly because lower voltage levels can reduce power consumption, reduce heat generation, improve integration, and also be compatible with new semiconductor technologies. These advantages have made 3.3V logic level gradually the preferred choice for some new devices and systems.
So, back to our question: Is RS232 5V or 3.3V? The answer is not a simple one or two choice. According to the original RS232 standard, the specified electrical characteristics are indeed based on a voltage range of ± 5 to ± 15 volts. This means that traditional RS232 interfaces use voltage swings above 5V to represent data signals. However, with the development of new technologies, some manufacturers have begun to offer low voltage versions of RS232 interfaces, which may use voltage swing of 3.3V or lower.
This change has brought some controversy and confusion. On the one hand, using low voltage swing can be better compatible with modern low-voltage logic circuits, reducing reliance on traditional 5V power sources. On the other hand, such changes may affect compatibility with existing devices, especially those designed with only 5V voltage swing considered.
In practical applications, the choice between 5V or 3.3V RS232 interface depends on multiple factors. If the user is connecting to an old RS232 device, a traditional 5V RS232 interface may be needed to ensure good compatibility and communication stability. If the connected devices are of the new generation and may support low voltage swing, a 3.3V RS232 interface can be chosen. However, even when using the 3.3V RS232 interface, compatibility measures on the circuit are usually designed, such as level converters or adapters, to ensure that the equipment is not damaged due to voltage mismatch.
The voltage level of RS232 standard is not fixed and unchanging, it evolves with technological progress and market demand. The traditional RS232 interface uses a voltage swing of 5V, while the new generation of devices may support voltage swings of 3.3V or even lower. When choosing the RS232 interface, users should decide which voltage level to use based on their device and application scenario, and take corresponding compatibility measures. With the continuous advancement of technology, there may be more variants of the RS232 standard in the future, but regardless, understanding its electrical characteristics and compatibility requirements will be the key to ensuring communication success.