Users can remotely open doors without incurring phone charges by calling or sending a text message, with support for up to 200 authorized users. The device allows remote control through an app, toll-free phone calls, and SMS, providing versatile operation options. The SM200 is a user-friendly and reliable GSM 4G remote switch controller, optimized with additional features for diverse scenarios. It includes authorization operation protection, ensuring only the main user can set authorized user access and operation times. The wide voltage power supply (DC9V-24V) features anti-reverse protection, enhancing safety and reliability., Manufacturer: Uxsjakjsd