Sealing current is also known in the telecommunications industry as wetting current. Sealing current may be sourced by the ATU-C in certain service providers that deploy “dry loop” DSL circuits, meaning that DSL is delivered in the absence of typical central office or remote terminal fed analog POTS service on the copper pair.

The following functional diagram depicts a sealing current circuit design specified in the IF.WAN.SEALING optional module that can be implemented on an xDSL residential gateway.