The **FNS-165-R** is a specific model of a **piezoelectric electronic siren/alarm**, commonly used in security systems, fire alarms, and industrial warning equipment. It is designed to provide high-decibel output with low power consumption. --- ## 1. Technical Specifications The following table summarizes the primary electrical and physical characteristics of the FNS-165-R: | Feature | Specification | | :--- | :--- | | **Rated Voltage** | 12V DC | | **Operating Voltage** | 6V - 15V DC | | **Current Consumption** | ~200mA to 300mA (at 12V DC) | | **Sound Pressure Level** | 105dB - 110dB at 1 meter | | **Tone Type** | Single Tone (Siren/Warble) | | **Material** | ABS Plastic (Flame Retardant) | | **Operating Temp** | -10°C to +55°C | --- ## 2. Key Electronic Components The internal circuitry of the FNS-165-R consists of three main stages that convert electrical energy into acoustic energy: ### A. The Oscillator Circuit Most units utilize a simple **transistor-based multivibrator** or a dedicated **siren IC** (like the NE555 or a COB - Chip on Board). This circuit generates the electrical frequency (usually between 2kHz and 4kHz) required to drive the sound element. ### B. Piezoelectric Transducer Unlike traditional speakers that use magnets and coils, the "R" in these series often refers to a **Piezoelectric element**. * **Piezo Ceramic Disc:** A ceramic layer bonded to a metal diaphragm. * **Function:** When the oscillating voltage is applied, the ceramic expands and contracts rapidly, vibrating the diaphragm to create sound waves. ### C. Driver Stage To achieve the high decibel (dB) output, a small **Step-up Transformer** or an **Inductor-based autotransformer** is often used. This boosts the 12V input to a much higher peak-to-peak voltage (often 40V-60V) to drive the piezo element at its resonant frequency for maximum volume. --- ## 3. Wiring and Installation The device typically features a simple two-wire interface: * **Red Wire:** Positive (+) terminal (Connect to 12V DC). * **Black Wire:** Negative (-) terminal (Ground). > **Note:** These devices are polarity sensitive. Reversing the wires will result in no sound, although most modern units include a protection diode to prevent circuit damage from reverse polarity. ---