Mercury Security has launched its S4 I/O Module family, a new generation of intelligent access control hardware designed to help organizations modernize and expand existing physical security infrastructure. The platform combines high-density door capacity, modular architecture, stronger cybersecurity and increased processing power while supporting forward and backward compatibility. The MR54-S4 Reader Interface Module provides four-door capability in the footprint of a previous two-door module, helping integrators increase capacity while reducing wiring complexity and equipment space.