The purpose of the Gate-keeper is the control of the RDCs, the ADCs, and the constant fraction discriminator. The Gate-keeper synchronizes the units and ensures that the data taking is clean and not intermixed with other events. There are six Gate-Keepers in the system, one for each proton detector. All input circuits are designed to accept TTL as well as negative NIM signals. The output is 50 ohm TTL or negative NIM as defined by internal jumpers.