Initiating a conference call includes receiving a conference call request message from an initiating user specifying a plurality of other users and determining an availability of the other users to receive conference call invitations. The metering surface has surface features, which are modified by buffing the metering surface. Stepwise application of a control signal to the appropriate switching elements forming an attenuator circuit may be implemented to moderate a switching time of the switching elements to provide a more gradual transition between element operating states.