Prepayment appliance for volumetric flow meters for gas or water supply

摘要

The appliance has a manual knob (5) to open a spring-closed valve (6) provided with loss of pressure protection. When a prepayment card is inserted in the opening (8), the valve can be opened manually, but only if the electronic circuit (10) confirms the card is in credit. The valve recloses when the credit is exhausted. The electronic system is powered by a power source adequate to cover the period between calibrations.