Trust me, this is what I do for a living. The line drivers are also inverters. A logic 1 is a low output, a logic 0 is a high output.
Or if you don't trust me check the wikipedia page on RS232:
Voltage levels
The RS-232 standard defines the voltage levels that correspond to logical one and logical zero levels. Signals are plus or minus 3 to 15 volts. The range near zero volts is not a valid RS-232 level; logic one is defined as a negative voltage, the signal condition is called marking, and has the functional significance of OFF. Logic zero is positive, the signal condition is spacing, and has the function ON. The standard specifies a maximum open-circuit voltage of 25 volts; signal levels of ±5 V, ±10 V, ±12 V, and ±15 V are all commonly seen depending on the power supplies available within a device. Circuits driving an RS-232-compatible interface must be able to withstand indefinite short circuit to ground or to any voltage level up to 25 volts. The slew rate, or how fast the signal changes between levels, is also controlled.
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