 In later 1AESS versions SD were solid state with several SD points per circuit pack generally on the same shelf or adjacent shelf to the trunk pack.A few peripherals that needed quicker response time, such as Dial Pulse Transmitters, were controlled via Central Pulse Distributors, which otherwise were mainly used for enabling (alerting) a peripheral circuit controller to accept orders from the Peripheral Unit Address Bus.The duplicate Harvard architecture central processor or "CC" (Central Control) for the 1ESS operated at approximately 200 kHz.