Plugboard

A plugboard is a panel of sockets connected by removable wires or plugs that configures an electromechanical machine by changing its circuits.

Patch panel: A panel of connectors used to route signals between equipment through removable cables. It shares the plugboard’s principle of configuring signal paths through physical connections.
Enigma machine: A German cipher machine that used rotors and a plugboard to encrypt and decrypt messages. Its plugboard exchanged pairs of letters, adding a configurable substitution to rotor encryption.
Telegraphy: Communication over distance by transmitting coded electrical signals. Electrical signaling established the switching practices that plugboard systems adapted.
Stored-program computer: A computer that stores instructions in memory alongside data or in addressable memory. It replaces rewiring as the main way to change a computer’s program.
Electrical circuit: A closed path through which electric current can flow. A plugboard changes which circuit paths a machine’s components form.
IBM 602: An IBM punched-card machine introduced in 1946 that performed multiplication and division. Its plugboard let operators specify how punched-card data flowed through arithmetic operations.
Telephone switchboard operator: A worker who manually connected telephone calls using a switchboard. Manual cord connections helped make configurable electrical routing familiar and practical.
Hardwired control unit: A processor control system whose operations are determined by fixed logic circuits. Its behavior is set by circuitry rather than by a removable wiring panel.
Relay: An electrically operated switch that opens or closes contacts in another circuit. Relays are common electromechanical components whose connections a plugboard can configure.
IBM 604: An IBM electronic calculating punch introduced in 1948 for commercial and scientific calculations. Operators programmed its control sequences by wiring a plugboard.

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