Every hotel has a room card. Only when the room card is inserted into the slot can the lights and sockets in the room have electricity. The room card is equivalent to a _ _ _ _ _ _ _ _ in the room.

(1) The room card can control the work of electrical appliances, and all the electrical appliances in the room do not work unless they are plugged into slots, so the room card is equivalent to a switch on the road;

(2) The switches in the home circuit should be connected in series with the controlled appliances, and the working conditions of the appliances do not affect each other, so the lights, televisions, air conditioners and other appliances in the room are connected in parallel.

(3) The voltage of the room circuit is the home circuit voltage, that is, 220 V. 。

So the answer is: switch and; 220.