This I-ETS specifies the eletroacoustic characteristics for handset functions implemented in videotelephony terminals intended for use in the videotelephone teleservice in the Integrated Services Digital Network (ISDN) using Adaptive Differential Pulse Code Modulation (ADPCM) encoding according to CCITT Recommendation G.722 [1]. Those terminals will be connected to the basic access of the coincident S and T reference point of the ISDN. The videotelephony teleservice in the ISDN is defined in ETS 300 264.