The **D4C0112S-R30A** is a specialized high-performance rotary switch manufactured by Electroswitch (specifically within their "D4" series). It is designed for demanding industrial and military-grade applications where reliability and high current capacity are required in a multi-deck configuration. --- ### ## Technical Specifications | Parameter | Value / Description | | :--- | :--- | | **Series** | D4 (Heavy Duty Rotary) | | **Number of Positions** | 12 Positions | | **Number of Poles** | 1 Pole | | **Number of Decks** | 1 Section (Deck) | | **Switching Type** | Shorting (Make-before-break) | | **Current Rating** | 0.5A @ 125VAC / 0.25A @ 250VAC | | **Voltage Rating** | Up to 125 VAC / 28 VDC | | **Termination Style** | Solder Lug | | **Contact Material** | Silver Alloy | | **Mounting Type** | Panel Mount | --- ### ## Key Electronic & Mechanical Components ### 1. The Rotor and Stator The switch utilizes a **Ceramic Stator**. Ceramic is chosen over phenolic or plastic materials because it offers superior insulation resistance and can withstand higher temperatures without warping. The rotor carries the common contact that moves between the 12 stationary terminals. ### 2. Shorting (Make-Before-Break) Mechanism The "S" in the part number indicates a **Shorting** configuration. - **Operation:** As you turn the knob, the moving contact touches the next position before it disconnects from the current position. - **Purpose:** This prevents "arcing" and ensures there is no momentary open circuit, which is critical in audio applications (to prevent pops) or power supply feedback loops. ### 3. Silver Alloy Contacts The contacts are typically made of a **Silver Alloy**. Silver provides the lowest electrical resistance, ensuring minimal voltage drop across the switch. The "R30A" suffix often denotes specific plating or indexing options (such as a 30-degree angle of throw between positions). ### 4. Indexing Mechanism The mechanical "click" felt when turning the switch is provided by a dual-ball side-thrust index mechanism. This ensures that the switch locks firmly into each of the 12 positions, preventing the switch from resting between contacts. --- ### ## Applications Because of its rugged ceramic construction and 12-position flexibility, this part is commonly found in: * **Test Equipment:** Multi-meter range selection. * **Communication Radios:** Frequency or channel selection. * **Industrial Controls:** Mode selection for heavy machinery. * **Audio Gear:** High-end gain stepping or input routing. ---