The electro-optical interfaces for the central and endcap calorimeters of the CMS experiment at the CERN Large Hadron Collider are readout boxes that receive optical signals via fiber-optic waveguides from the calorimeter scintillator megatiles that comprise the active elements of the detector and decode these signals for energy measurement. The phototransducers housed within the readout boxes are Hybrid Photodiodes (HPDs) which detect and amplify the optical signals. Digitization is provided by preamplifiers or by QIE (Charge, Integration, and Encode) chips. Output signals are then transmitted from the readout boxes to Trigger/DAQ systems located off-detector. Design concepts and construction details are presented for the first pre-production-prototype readout boxes.