The present invention provides a security system for controlling access of persons through a controlled portal. The portal, such as a door, has a lock mechanism for securing the door. A presence detector senses the presence of an object within an approach zone located substantially adjacent the portal. When an object is detected, a fixed transceiver automatically transmits an interrogation signal into the approach zone. A portable transceiver is carried by the person seeking access to the portal. The portable transceiver responds to the interrogation signal by transmitting a response signal. Each portable transceiver or group of transceivers has a unique identification code which is included in the response signal. The fixed transceiver receives the response signal and determines whether the response signal contains a valid access code. If a valid access code is received, the portal is unlocked and other devices may be activated.