A network interface device includes a first interface operable to receive at least two incoming calls over a subscriber line, and a second interface operable to facilitate communication between the first interface and a first telephone line and between the first interface and a second telephone line. The second interface is also operable to generate one or more first ring voltages on the first telephone line and one or more second ring voltages on the second telephone line. The network interface device also includes a processor coupled to the first interface and the second interface. The processor is operable to instruct the second interface to generate the first and second ring voltages in response to receiving the incoming calls. The processor is also operable to allocate the first and second ring voltages among the first and second telephone lines to ensure that a total instantaneous load placed on the second interface does not exceed a determined threshold level.