Abstract: A security system for detecting weapons and explosives being carried into buildings and similar locations accessible to the public. A sensing unit is located at a monitored premises, and has at least two types of sensors. Each sensor senses a characteristic of weapons or explosives which is different from characteristics sensed by another sensor. The sensing unit transmits data signals by radio to a control station having a microprocessor for processing these data signals. Data from the sensing unit is compared to stored data relating to known, predetermined characteristics of weapons and explosives. If comparison determines recognition of a weapon or explosive or both at a monitored premises, an alarm ensues. Identification of the weapon or explosive is displayed on a CRT monitor and is printed out. Optionally, a distress signal is generated, and connected by a telephone system to a third party. Preferably, many sensing apparatuses at diverse premises communicate with a single control station.