In a level sensor having a pair of measuring electrodes and a pair of reference electrodes, reference electrodes have a horizontal section. These polymer compositions, which are also characterized by superior compatibility with water-based and solvent-based adhesives, comprise at least one thermoplastic elastomer and at least one maleated ethylene copolymer. An operating mechanism is mounted on the surrounding structure, rather than on the panel, to retain the panel in the closed position. The multi protocol system employing the RTP provides a single RTP control interface for transmitting and receiving audio packets to completely manage the system totally and raises a degree of resource utilization of the system by making it easy to implement additional functions to the RTP and coder through the buffers.