This diagram shows the wiring for a new receptacle added from a light switch. The switch must have an always-hot wire for the source and a neutral wire must be present for the return path. The hot source is spliced with a pigtail back to the switch, and to a new 2-wire cable running to the new outlet. The neutral is spliced in the switch box to both the existing light, and the cable to the new receptacle.
Here 3-wire cable serves a split receptacle. The bottom half of the receptacle is controlled by a switch and the top half is always-hot.
This diagram illustrates wiring for a circuit breaker with a built-in ground fault circuit interrupter. This 20 amp ground fault interrupter breaker is a form of gfci that can be installed at the circuit source. This kind of circuit is used for dishwashers, whirlpool spas and other locations where water contact is likely.
It’s not unusual for an old house to have an old doorbell lurking about somewhere that hasn’t worked in years. Fortunately, it’s likely a simple matter to get things back in working order. As illustrated in the above diagram, the parts of an old doorbell circuit include the bell, a button mounted at the door, and a battery somewhere in between the two.