An alarm includes a chain guard assembly in which a slide member is attached to a door jamb by a chain and is removeably engaged in a slot member which is mounted on the inside of a door. An alarm enclosure which is connected to the slot member includes an alarm and a battery. A normally open switch assembly is mounted on the slot member. Movement of the slide member caused by a forced opening of the door causes the slide member to bear against the switch assembly causing the switch assembly to close and complete an electrical circuit between the battery and the alarm thereby activating the alarm.
