Components that earn their place.

An AA battery holder (single-cell) is a small plastic holder designed to securely hold one AA-size battery.

A 3-cell rechargeable battery holder is a plastic holder designed to securely hold three rechargeable batteries, commonly 3.7V Li-ion cells.

A 1-cell rechargeable battery holder is a plastic holder designed to securely hold one rechargeable battery, commonly a 3.7V Li-ion battery.

A 2-cell rechargeable battery holder is a plastic holder designed to securely hold two rechargeable batteries and provide electrical connections to a circuit.

A small buzzer is an electronic component that produces a beeping or buzzing sound when electrical power is supplied to it.

A standard electronic power supply that converts household AC voltage (100–240V) into a stable 12-volt DC output at up to 2 amperes (24 watts). It typically features a 5.5mm x 2.1mm or 5.5mm x 2.5mm center-positive barrel connector.

A 9V 2A power adapter is an electrical device that plugs into a standard wall outlet (100V–240V AC) and converts it into a stable 9-volt direct current (DC) output capable of supplying up to 2 amps (18 watts of max power).

A 5V 2A power adapter is a 10-watt electrical device that converts AC wall power (100V–240V) into a steady 5-volt DC output with a maximum current of 2 amps.