Otoscope and telephone: what they have in common

1. Step 1. Otoscope — has part — LED. Illumination.
2. Step 2. LED — is part of — Traffic light. LEDs.
3. Step 3. Traffic light — has part — Relay. Relay controllers.
4. Step 4. Relay — is part of — Telephone exchange. Relay switching.
5. Step 5. Telephone exchange — is used in — Telephone. Connecting subscribers.

Open Evothings