The MAX232 is a dual driver/receiver that includes a capacitive voltage generator to supply RS-232 voltage levels from a single 5V supply. Each receiver converts RS-232 inputs to 5V TTL/CMOS levels. These receivers have a typical threshold of 1.3V, a typical hysteresis of 0.5V, and can accept ±30V inputs.
Please note that there may be variations in the Typical Operating Circuit depending on the MAX232 model. Therefore, it is advisable to refer to the corresponding datasheet for accurate information. Commonly, there may be variations in the charge-pump capacitors.