Doorbell / Chime Symbol
Definition: The Doorbell / Chime symbol represents the sounder or chime unit in a residential low-voltage doorbell wiring diagram, depicting the device that produces an audible alert when a remote pushbutton is pressed, shown as a bell or speaker symbol with a Transformer terminal and a Button terminal corresponding to the two low-voltage input connections from the doorbell transformer and pushbutton circuit respectively.
Also known as: door chime, door bell, chime unit, doorbell sounder, doorbell receiver, bell chime.
What the Doorbell / Chime symbol means
The Doorbell / Chime symbol marks the location of the sound-producing unit in a doorbell wiring diagram, typically mounted indoors (hallway, kitchen, or living area) where occupants can hear the alert. The symbol indicates the chime box that receives a low-voltage signal from the pushbutton and converts it into an audible tone, melody, or mechanical bell strike.
In residential wiring diagrams the Doorbell / Chime symbol connects to two conductors: the Transformer pin receives the stepped-down AC voltage from the doorbell transformer (typically 8 V, 16 V, or 24 V AC), and the Button pin connects the switched circuit from the front-door pushbutton. When the pushbutton is pressed, it completes the circuit between the transformer output and the chime, energising the chime solenoid or electronic tone generator.
How to identify the Doorbell / Chime symbol
The Doorbell / Chime glyph is drawn as a bell silhouette (a curved profile with a small clapper symbol) or a speaker symbol, sometimes enclosed in a small rectangle representing the wall-mount chime unit box. The two connection points are the Transformer pin (incoming AC power) and the Button pin (switched signal from the pushbutton). In simplified wiring diagrams a simple rectangle labelled 'CHIME' or 'BELL' with two terminals is commonly used. The symbol is distinguished from a buzzer (which typically shows a more angular or zigzag element) and from a horn (which shows a megaphone profile) by its bell or speaker shape.
Function in a circuit
The doorbell chime unit converts a brief low-voltage electrical pulse—produced when the doorbell pushbutton closes the circuit—into an audible signal. Mechanical chime units use a solenoid striking a set of tuned metal bars (Westminster, two-tone, or single-tone chimes). Electronic chime units use a microcontroller to play a stored melody through a small loudspeaker. Smart/video doorbell units additionally include the chime function either via a wired indoor chime or through a wireless notification to a smartphone app.
Standards: IEC vs ANSI
| IEC 60617 | IEC 60617 includes a bell or buzzer symbol in the signalling device category; a doorbell chime is represented by the bell symbol or a generic sounder symbol. Low-voltage doorbell systems in IEC-territory installations typically operate at SELV (Safety Extra-Low Voltage) per IEC 61140, at 8–24 V AC from a Class 2 (IEC) transformer. |
|---|---|
| ANSI/IEEE 315 | ANSI Y32.2 / IEEE 315 includes a bell symbol for signalling devices. NEC (NFPA 70) Article 725 governs Class 2 and Class 3 circuits including residential doorbell wiring; the transformer and associated wiring must comply with Class 2 low-voltage wiring requirements. |
| Key difference | IEC and ANSI symbols for doorbell chimes are functionally the same bell or speaker glyph. NEC Article 725 specifies Class 2 wiring rules for the low-voltage wiring from transformer to pushbutton and chime; IEC 61140 specifies SELV requirements. The schematic symbol is identical in both regions. |
Terminals / pins
| Pin | Name |
|---|---|
| trans | Transformer |
| button | Button |
Typical values
Operating voltage: 8 V, 16 V, or 24 V AC (most common: 16 V AC in North America). Transformer VA rating: 5 VA to 40 VA. Chime current draw: 100 mA to 500 mA during strike. Wiring: 18 AWG or 20 AWG two-conductor or three-conductor low-voltage bell wire. Smart doorbells: 16–24 V AC, 40–200 mA continuous.
Where the Doorbell / Chime symbol is used
- Residential front-door and back-door entry notification in single-family homes and apartments
- Multi-unit residential buildings with individual apartment chime units wired from a common entry panel
- Small commercial offices using a simple door-entry alert without a full intercom system
- Retail shops with a door-entry chime alerting staff when customers enter
- Home workshop or garage notifications alerting the occupant of visitors while working away from the main door
- Assisted-living and care facilities providing gentle audible door alerts for residents with hearing aids
Example
In a residential doorbell wiring diagram, the Doorbell / Chime symbol is mounted in the hallway; the Transformer pin is connected via 18 AWG bell wire to the 16 V AC secondary terminal of a doorbell transformer mounted in the attic. The Button pin connects via a second run of 18 AWG wire to the Doorbell Button symbol at the front door. When the pushbutton is pressed it completes the circuit, current flows through the chime solenoid, and the chime strikes a two-tone melody.
Key facts
- The Doorbell / Chime symbol has two terminals: Transformer (connected to the low-voltage AC supply from the doorbell transformer) and Button (connected to the switched wire from the pushbutton); the chime is energised when the Button circuit is completed.
- Residential doorbell systems operate at SELV voltages—typically 8 V, 16 V, or 24 V AC—supplied by a step-down transformer connected to the 120 V or 230 V mains supply; the low-voltage wiring is governed by NEC Article 725 (Class 2) in North America and IEC 61140 SELV requirements internationally.
- Mechanical chime units use a solenoid plunger striking metal bars tuned to specific notes (Westminster four-note or two-tone chimes); the solenoid is energised momentarily by the pushbutton press.
- Electronic (digital) chime units store multiple melodies in firmware and allow selection of different tones per pushbutton location (front door vs. rear door), enabling differentiation between multiple entry points.
- Smart doorbell systems (e.g., Ring, Nest) can connect to an existing wired chime unit using the same 16–24 V AC transformer wiring, adding video and Wi-Fi connectivity alongside the conventional audible chime function.
- Three-conductor bell wire is used when two pushbuttons (front and back door) are connected to the same chime unit: one conductor is common (from transformer), one goes to the front-door button, and one to the back-door button.
- The doorbell transformer must be rated for the VA demand of the chime unit plus any additional smart doorbell electronics; undersized transformers cause voltage drop, chime misfires, or buzzing.
Diagrams that use this symbol
- doorbell wiring diagram
- door bell wiring diagram
- buzzer circuit diagram
- doorbell transformer wiring diagram
- doorbell chime wiring diagram
- 4 wire doorbell wiring diagram
- doorbell circuit diagram
- single doorbell wiring diagram
Frequently asked questions
What does the doorbell / chime symbol mean in a wiring diagram?
The Doorbell / Chime symbol represents the indoor sound-producing unit in a doorbell wiring circuit—the device that rings, chimes, or plays a melody when the remote pushbutton is pressed. It indicates the chime box location and its two electrical connections: the transformer supply and the pushbutton-switched circuit.
What does the doorbell chime symbol look like?
The Doorbell / Chime symbol is typically drawn as a bell silhouette with a small clapper, or as a speaker profile, sometimes enclosed in a rectangle representing the wall-mount unit. Two terminals—Transformer and Button—are shown as connection points. Simplified diagrams may use a rectangle labelled 'CHIME' or 'BELL' with two terminals.
What are the Transformer and Button terminals on the doorbell chime symbol?
The Transformer terminal is the pin connected to the low-voltage AC output of the doorbell transformer (typically 16 V AC), providing the chime's operating power. The Button terminal is connected to the wire from the front-door pushbutton; pressing the pushbutton completes the circuit between the transformer and the chime, energising the solenoid or tone circuit.
What voltage do doorbell chimes operate on?
Doorbell chimes typically operate at 8 V, 16 V, or 24 V AC supplied by a small step-down transformer connected to the household mains. The most common North American voltage is 16 V AC. This low voltage is classified as SELV (Safety Extra-Low Voltage) and is governed by NEC Article 725 (Class 2 circuits) or IEC 61140.
What is the difference between a doorbell chime and a doorbell buzzer?
A doorbell chime produces a musical tone (single note, two-tone, or multi-note melody) using a solenoid striking tuned metal bars or an electronic tone generator. A buzzer produces a continuous or pulsed buzzing tone using a vibrating reed or piezoelectric element. The chime symbol shows a bell or speaker shape; the buzzer symbol shows a more angular zigzag or piezo indicator.
Can I use the existing doorbell wiring with a smart video doorbell?
Yes. Most smart video doorbells (Ring, Nest, Eufy) are designed to connect to existing 16–24 V AC doorbell wiring and can power both the smart doorbell camera at the front door and the existing indoor chime unit simultaneously, provided the transformer is rated for at least 30–40 VA to supply the additional electronics. Some smart doorbells include a bypass adaptor to work with mechanical chime units.
What NEC code governs doorbell wiring?
Doorbell wiring is governed by NEC (NFPA 70) Article 725, which covers Class 2 and Class 3 remote-control and signalling circuits. Class 2 circuits at 30 V or less (such as doorbell wiring) have reduced wiring requirements compared to power circuits, allowing smaller wire gauges (18–22 AWG) and simplified wiring methods. The doorbell transformer must be listed and must be permanently connected to a branch circuit.
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