单项选择题 If both the “high level” and “low level” alarms come on for the same address of a centralized control console, the most likely problem is a/an （）.

单项选择题 For practical purposes, in a simple series circuit, the source voltage will be dropped across one resistor if it has（）.

单项选择题 Which is a function of the voltage regulators used with AC generators?（）