An adapter block assembly includes an adapter block, a circuit board arrangement, and a cover attached to the adapter block so that the circuit board arrangement is held to the adapter block by the cover. Contact assemblies can be disposed between the adapter block and the circuit board arrangement. The cover can be latched, heat staked, or otherwise secured to the adapter block. Each component of the adapter block assembly can include one or more parts (e.g., multiple adapter blocks, multiple circuit boards, and/or multiple cover pieces).