The term **7201D** typically refers to a specific series of **Miniature Toggle Switches** manufactured by companies like C&K (now part of Littelfuse). These are staples in the electronics industry for PCB mounting and manual control interfaces. --- ## 1. Technical Specifications (General) The "7201" prefix identifies the functional configuration of the switch, while the "D" suffix often denotes the specific terminal or bracket style (though this can vary slightly by manufacturer). | Feature | Specification | | :--- | :--- | | **Circuit Type** | DPDT (Double Pole Double Throw) | | **Switch Function** | ON-ON (Two positions, both maintained) | | **Contact Rating** | Usually 5A @ 120V AC or 2A @ 250V AC | | **Contact Resistance** | 10 mΩ max. initial | | **Insulation Resistance** | 1,000 MΩ min. | | **Dielectric Strength** | 1,000 Vrms min. at sea level | | **Operating Temp** | -30°C to +85°C | --- ## 2. Component Structure A 7201D switch is comprised of several critical electronic and mechanical parts: ### A. The Actuator (Toggle) The lever moved by the user. It is usually made of chrome-plated brass or stainless steel. In the 7201 series, these come in various lengths (Standard, Short, or Flatted). ### B. The Internal Contacts * **Movable Contact:** A "C-spring" or "seesaw" mechanism that snaps between positions to ensure a fast, clean electrical break/make. * **Stationary Terminals:** Usually silver-plated or gold-plated copper alloy. Gold is preferred for low-power (logic level) applications to prevent oxidation. ### C. The Housing (Case) Typically made of **Diallyl Phthalate (DAP)** or high-temperature glass-filled nylon. These materials are chosen for their high flame retardancy (UL 94V-0) and heat resistance during soldering. --- ## 3. Circuit Configuration: DPDT The "7201" designation specifically indicates a **Double Pole Double Throw** configuration. ```text Terminal Layout: [ 1 ] [ 4 ] <-- Pole A & Pole B [ 2 ] [ 5 ] <-- Common A & Common B [ 3 ] [ 6 ] <-- Pole A & Pole B ``` * **Position 1:** Terminals 2-1 and 5-4 are connected. * **Position 2:** Terminals 2-3 and 5-6 are connected. * **Application:** Useful for reversing the polarity of a DC motor or switching two independent signals simultaneously with one flip. --- ## 4. Part Number Breakdown (Example: C&K Series) | Segment | Meaning | | :--- | :--- | | **72** | Series (7000 Series Miniature Toggle) | | **01** | Function (DPDT, ON-ON) | | **D** | Terminal Style (Right angle, PC thru-hole, or Wire wrap depending on catalog) | | **(Suffix)** | Contact material (e.g., Q = Silver, B = Gold) | ---