Abstract

A home security and garage door operator system includes a gas sensor for detecting the level of toxic gas in the garage. When the gas level exceeds a predetermined threshold the garage door is automatically opened. Lock out circuitry is provided for preventing the door from being accidentally closed as long as the gas sensor detects an excessive level of toxic gas in the garage. A two button transmitter is used to sequentially close the garage door and set a security alarm subsystem. Warning devices are activated if the security alarm is attempted to be set without the garage door and windows in the home being closed. Once the security alarm has been set, the lock out circuitry also disables the garage door motor control circuitry until the security alarm is first deactivated. The transmitter generates a digital pulse train according to a preselected code, with the operation of the dual buttons changing the state of a particular control bit in the pulse train. A central control module in the garage includes a receiver with channel monitoring circuitry designed to detect the state of the control bit to initiate different functions, for example, the setting of the security alarm and the actuation of the garage door. The system further includes a heat sensor in the central control module and advantageously uses a line carrier to transmit status information regarding the monitored parameters to a remote module in the home. A maximum run timer and motor overload protection for the motor control circuitry are also disclosed.