The D SERIES-HA1A is a two pair receiver and audio headphone amplifier compatible with RDL Format A twisted pair products. Each -HA1A receives stereo audio and 24 Vdc power through a rear-panel RJ45 jack fed from a Format-A sender. The left and right audio signals received on pairs B and C of the twisted pair cable are amplified and fed to the left and right channels of the output 3.5 mm Mini-jack.