Answer:
B.
Explanation:
Battery
A station battery voltage of 24–48 volts dc is supplied from the central office (the term battery is used regardless of the source of the voltage). The ring wire is negative with respect to the tip, but modern telephone instruments are insensitive to the polarity of the applied voltage. The battery voltage is used to power the telephone instrument and to provide current that indicates an off-hook condition. Current is limited to prevent wire heating and personal injury, and to protect the central office against shorts on a line. In the case of a cable telephony system, the network interface device provides this voltage.
