Abstract: A security system includes a plurality of sensors each capable of providing a detection input signal adapted to cause activation of the alarm system, a circuit for inhibiting activation of the alarm system as a result of a first detection input signal, and a circuit for removing the inhibition and allowing activation of the alarm system in response to a second detection input signal from any one of the sensors, including the sensor that provided the first detection input signal. A first alarm device is located essentially indoors on the premises to be protected and a second alarm device is located outdoors on the premises to be protected. The inhibition circuit allows activation of only the indoor alarm device, but a further detection input signal from one of the sensors within a predetermined time activates the outdoor alarm device.

Abstract: A monitoring system of the type suitable for use in monitoring signals from security installations or networks includes a central control station serving a plurality of users and to which the users are connected by an existing telephone network or some other form of direct or switched line connection. Each user is provided with an encoder in the form of a combined control unit and digital telephone dialler, said encoder being programmed with information concerning each user in principally alphabetical character form to increase the likelihood that the message will be received and understood even in the event that certain characters contained in the message are missing. The control station is equipped with means for receiving and decoding the message transmitted from the user's control unit together with visual display means, such as a VDU or line printer, for visually displaying the received message.