A specialized telephone circuit designed to automatically ring a specific destination as soon as the user goes off-hook. Historically, lifting the receiver dropped a relay at the operator's switchboard, triggering a physical indicator and a bell. In later automatic exchanges and private networks, ringdown circuits are programmed as direct point-to-point lines without dial tones, used primarily for emergency phones, financial trading desks, and secure command links.
Heard on the job
We need to provision a ringdown circuit between the control room and the backup generator facility.
Insider tip
Technicians often refer to any direct, dial-less emergency phone as a ringdown, even if it is routed via VoIP rather than a physical copper tie line.
Also heard as
- automatic ringdown
- ARD
- batphone