The Key Processing Unit (KPU) and Lock Programming Unit (LPU) are the interfaces between the Quantum Plus software and the INTELLIKEY Intelligent Keys and Locks. These devices allow the software to program, update and interrogate the components of the ACS4000 system.

The KPU and LPU connect to the PC through a standard serial port, or through an optional USB-to-serial adapter. The KPU may also be connected through a network interface or modem to allow to allow remote updating or auditing of keys.