Circuit arrangement for energizing an electromagnet in a coin-freed telephone station

摘要

A pulse generating circuit (12) generates two current pulses (d and e) which immediately follow one another. The amplitude and duration of the first current pulse (d) are sufficient for attracting the armature of the electromagnet (21), the amplitude of the second current pulse (e) is only sufficient for holding the attracted armature and its pulse duration corresponds to a predetermined period during which the armature is to be held in the attracted position. A feed circuit (1, 2) fed from the subscriber line (3) supplies two voltages of different magnitudes, the higher voltage being applied to a switching transistor (31) of the section (11) of the pulse generating circuit (12) switching the first current pulse (d) and the lower voltage, which is a fraction of the higher voltage, being applied to a switching transistor (14) of the section (15) of the pulse generating circuit (12) switching the second current pulse (e). As a result, the electromagnet (21) can be fed with minimum power consumption from the subscriber line. IMAGE