The document describes two models of HD encoders from Blonder Tongue Laboratories:
(1) The HDE-2H-QAM accepts two HDMI or YPbPr inputs, encodes them into a high-definition stream, multiplexes the streams into one QAM output.
(2) The HDE-2C-QAM is identical but only accepts two YPbPr inputs.
Both models digitize, encode, and multiplex up to two analog or digital video sources into a single digital QAM RF output suitable for cable television systems.