-# Setting RS-232 signals, like DTR and RTS, from a host using Python using the
-# convention defined above:
-# A signal is asserted by calling serial.setXXX(1) [Ex: setDSR(1)]
-# A signal is unasserted by calling serial.setXXX(0) [Ex: setRTS(0)]
+# RS-232C signals are active low. Confusingly, however, RS-232C physical
+# drivers effectively invert the value, such that a high value, or MARK, is
+# delivered over the wire as a negative voltage while a low value, or SPACE, is
+# delivered as a positive voltage. By looking at an RS-232C signal on an
+# oscilloscope, one might conclude that the RS-232C signals are active high for
+# this reason. Here is how RS-232 breaks down: