OHS is open Arduino based burglar alarm and automation platform. It can work as new alarm gateway, or it can replace your old alarm panel. OHS can use any wired 12V sensor, PIR, smoke or reed switch. It has Web interface that is used to set it up. OHS has GSM modem that is able to send SMS or page you. It has radio interface for environmental sensors. OHS is self-contained, it does not need any cloud service, only optional SMTP server for emails, or MQTT to publish collected sensor data.