The invention concerns inclusion complexes of precursors from a natural source of organic isothiocyanates, in particular having bacteriostatic, bactericidal andor fungicidal properties, in cyclodextrins. The amplifier has a first input which receives an input signal, a second input coupled to the reference node, and an output which provides an output signal having first and second states indicative of the input signal. The electronic control device makes use of the solution of an equation which relates the mass flow rate of the refrigerant fluid to the difference in pressure between the first point and the second point in order to calculate an estimate of a magnitude relating to the refrigerant fluid. Identity claims may include addresses, phone numbers, instant messenger addresses or other contact data that is likely to be uniquely associated with a contact.