Abstract: System for asymmetrical signal transmission from a pair of transmission devices (AT,VT) through a pair of signal paths (ASL, ARL; VSL, VRL) each having at least one signal line (ASL, VSL) and one reference line (ARL, VRL) to a pair of receiver devices (AR', VR), two devices (AT, VT) of which having a supply reference potential (G1) in common and being coupled to one end of each of the two signal paths (ASL, VSL), and the other two devices (AR', VR) of which having a further supply reference potential (G2) in common and being coupled to the other end of each of the two signal paths (ASL, VSL).

Abstract: A device for converting an electric signal into an acoustic signal, which comprises an electro-acoustic transducer unit (2) having a quality factor (Q) less than unity. The device further comprises an amplifier circuit (3) for driving the transducer unit. The amplifier circuit has a frequency-dependent gain characteristic (6) which increases towards the lower frequencies, starting from f.sub.2, in a frequency range between a first and a second frequency (f.sub.1 and f.sub.2), f.sub.1 being the resonant frequency of the transducer unit (2) and f.sub.2 being greater than f.sub.1. The efficiency can be increased if amplifier the circuit includes a special amplifier such as a switched amplifier, for example, a class-D amplifier, or an amplifier with a power supply that provides a DC voltage that depends on the drive level of the amplifier.

Abstract: A device for driving an electroacoustic transducer (1) comprising a feedback amplifier and a pickup (2) whose output signal is a measure of the acoustic output signal of the transducer. A by-pass network (4) bypasses at least the transducer and the pickup and produces an output signal that for frequencies outside the operating range of the transducer is large and for frequencies in the operating range (f.sub.1 to f.sub.h) of the transducer is small relative to the pickup output signal. The sum of the output signals of the pickup and the by-pass network serves as a feedback signal. This widens the transducer frequency range and reduces distortion. The device may include a limiter (11) and a network (5) before the transducer. The network has a frequency response inverse to that of the signal path from the electroacoustic transducer to the pickup to provide an additional reduction in the distortion.