u 81xx

... Input and Accessory Identification U low U high Description 1.15 V 1.4 V ... EXT_RF: External RF Control Input U low U high Description 0.0 V 0.5 V ... in use MBUS: Serial Control Bus U low U high Description 0.0 V 0.5 V ... External Speaker and Mute Control U low U high Description 0.0 V 0.5 V ... (HF Speaker Active) Hook: Hook Signal U low U high Description 0.0 V 0.5 V