The CQ-K557 is a straight key with a built-in practice oscillator, designed for Morse code training and transmission. It delivers precise keying and clear tones, making it ideal for both practicing and sending accurate signals. A switch on the top-right corner allows you to turn the oscillator ON or OFF, with no sound produced when set to OFF. Two silver knobs provide adjustable keying amplitude and spring tension, though they do not affect volume or tone. The mahogany base features non-slip rubber pads, making it lightweight (only 230 g) and portable. The key supports audio simulations with adjustable touch points, suitable for telegraph and telegraphy training. For standalone practice, a coin cell battery (not included) powers the oscillator, which emits both sound and a red light, while connection to a radio via an audio cable eliminates the need for a battery. A 3.5mm female to 6.5mm male audio cable adapter allows easy installation in radios with a 6.5mm audio connector. The CQ-K557 is vacuum-packed to prevent oxidation, ensuring long-lasting performance and reliability. Features/ Technical Specifications: Code Key Type: Straight key Code Key Connector: 3.5mm audio connector Weight: 230g Code Key Base Size: 11.5*6.5*2cm Packing Box Size: 13*6.5*5cm Attached Accessories: CQ-K557 straight key 3.5mm audio cable 3.5 female to 6.5 male audio cable adaptor NOTE: Coin cell battery is not included in product set