What should a meter read when measuring a POTS with the phone off the hook?

When measuring the voltage of a Plain Old Telephone Service (POTS) line with the phone off the hook, it should typically read between 7 to 9 volts DC. This voltage range indicates that the phone line is in a state of providing power to the phone while it is actively connected and "off the hook."

The reason this range is significant is that it reflects the line voltage that the phone company supplies for operational functions, such as ringing and powering the phone. When the phone is off the hook, it draws power, and the voltage tends to stabilize within this appropriate range.

Other voltage readings would not indicate a proper functioning telephone line under this condition. For example, readings considerably lower than this range might suggest that there is an issue with the telephone line, such as a disconnection or fault in the wiring that could prevent the phone from operating correctly.