Abstract: The energy of the sound radiation caused by the impact of the coin to be analyzed upon a hard surface is split into different frequency bands, the energy of every such band is obtained and the ratios between them are then worked out, obtaining parameters that are then compared against values representing valid coins. The device includes a bank of filters (6, 7 and 8), integrators (9, 10 and 11) connected to the outlet of the filters and capable of being activated from a microprocessor (17) and an analogue-digital converter to which the output of the various integrators is then connected through a multiplexer.

Abstract: The systems consists of an intrinsic collaboration among a message concentrator unit, a center operating unit, several visual displays, printers, information storage devices including operating and management software, insuring that modular telephones and both validation and identification units and access units control together with regional billing centers and a validation and billing center, as well as terminals of collecting entities by interchanging diverse specific operating messages within the public modular telephone management system-the whole context and operation arisen from their performance.