Subscriber handset with acoustic number selection indication - provided by piezoelectric transducer also producing acoustic call signal

摘要

The subscriber handset has a piezoelectric transducer (PZ) for providing an acoustic call signal and which is connected in series with a control element (T1) for charging and discharging it in dependence on an input signal obtained from the call current. During a number selection operation, a second input signal is supplied via a switch (S) directly to the control element (T1), so that the piezoelectric transducer (PZ) provides an audible indication of the number selection. Pref. the control element (T1) comprises a transistor, with a second transistor (T2) connected in parallel across the piezoelectric transducer (PZ), for discharging it when the control element (T1) is blocked.