A modular security, monitoring, and control device having a core module, an input/output module, a first peripheral, a first end cap, and a tamper monitor. The core and input/output modules in electrical communication with one another. The first peripheral is removably connected to the core module so that the core module and the first peripheral are in electrical communication. The first end cap is removably connected to the first peripheral. The tamper monitor detects tampering with the first peripheral.