Cardiopulmonary resuscitation and programmable logic controller: what they have in common

1. Step 1. Cardiopulmonary resuscitation — uses — Defibrillator. Defibrillation.
2. Step 2. Defibrillator — has part — Transformer. Stepping up the voltage.
3. Step 3. Transformer — has part — Copper wire. Windings.
4. Step 4. Copper wire — is part of — Electrical telegraph. Communication lines.
5. Step 5. Electrical telegraph — has part — Relay. Relays boosted the signal on long lines.
6. Step 6. Relay — evolved into — Programmable logic controller. It replaced relay cabinets.

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