Phone line jack and transformer: what they have in common

1. Step 1. Phone line jack — is part of — Modem. Connection to the telephone line.
2. Step 2. Modem — uses — Telephone. It works over a telephone line.
3. Step 3. Telephone — evolved from — Electrical telegraph. The telephone grew out of attempts to send several signals over telegraph lines (the “harmonic telegraph”).
4. Step 4. Electrical telegraph — has part — Copper wire. Communication lines.
5. Step 5. Copper wire — is part of — Transformer. Windings.

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