SCADA and bell: what they have in common

1. Step 1. SCADA — uses — Programmable logic controller. Polling the controllers.
2. Step 2. Programmable logic controller — evolved from — Relay. It replaced relay cabinets.
3. Step 3. Relay — has part — Electromagnet. An electromagnet switches the contacts.
4. Step 4. Electromagnet — is part of — Electric bell. An electromagnet strikes a small hammer.
5. Step 5. Electric bell — is part of — Alarm clock. A bell.
6. Step 6. Alarm clock — has part — Bell. A bell rings.

Open Evothings