A security system and display module therefore protects an item of merchandise mounted on the display module in a retail environment. The item of merchandise is electrically and mechanically connected to a sensor which is removably mounted on the display module by a first power cord. A second power cord connects the display module to the sensor and a third power cord connects the display module to a source of electricity for supplying electric power to the sensor through the display module and then to the displayed item for maintaining the charge on a battery of the displayed item. The display module contains an alarm unit having an audible alarm which is actuated if the integrity of either of the first or second power cords is compromised. A plunger switch and LED may be contained in the sensor and in a base of the display module and connected to the internal alarm to provide additional security for the protected item of merchandise. The alarm is powered from the source of electricity but is automatically switched to the battery upon interruption of this power source.