This is a Digital Multimeter, a device used by electricians and electronics technicians to inspect and measure electricity. It can measure: * Electrical voltage (AC/DC Volts). * 🔋 Electrical current (Amperes). * 🔧 Resistance (Ohms Ω). * 🔔 Wire continuity test (emits a beep if the wire is intact). * ➡ Diode test. * 📶 Frequency measurement (Hz). The device you have is from the Japanese company Sanwa, model CD800a, and is considered one of the good devices known for its accuracy and reliability.