A perimeter security system includes a barrier and a series of sensors. The sensors are connected together via connection cables that include pin-type engagement structure for connection with the sensors. The sensors may include a graduated sensory alert that changes as a person or object approaches. The pin-type connection arrangement includes a receiver having a passage for receiving an insert. The insert and a first end of the cable have matching cross-sections that enable the cable to be inserted within the receiver in a single orientation. A series of pins extend from the cable, and a pin contact arrangement is associated with the receiver. The insert may be one of at least a pair of differently configured inserts, each of which has a cross-section that matches only one end of the cable. Each insert includes an end wall, which includes a series of openings through which the pins extend.