When the conversation is not heard in a voice intercom but the buzzer and door lock work then the most probable fault is a damage in the power supply unit a. True b. False Under which of the following conditions will a diac stop conducting a. When the current between its terminals falls under the value of its holding current b. When either the voltage falls under the value the break over voltage or the current falls under the value holding current c. When the voltage across its terminals falls under the value of its breakover voltage d. When the gate current is zero One of the following statements is true regarding the earth leakage circuit breaker a. It is a device mainly used to protect devices from short-circuits b .when its test push button is pressed, it will be activated even though the power is off It cuts off power due to imbalanced currents in phase coil and neutral coil d. It prevents electric shock even an earthing system is not provided