These electronic subscriber loop interface circuits (SLICs) are optimized for low power consumption while providing an extensive set of features. The SLICs include an auxiliary battery input and a built-in switch. In short-loop applications, they can be used in high battery to present a high on-hook voltage, and then switched to low battery to reduce offhook power. The SLICs also include a summing node for meter pulse injection to 2.2 Vrms. A spare, uncommitted op amp is included for meter pulse filtering. The switched battery is applied to the power amplifiers of the device. There are two versions. The L7556 has the battery switch completely under processor control. The L7557 can automatically switch to lower battery when appropriate and includes hysteresis to avoid frequent switching. To make the switch silent, an external capacitor can be added to slow the transition. The L7556 is suited for applications serving only short loops, where a high on-hook voltage is required for compatibility with preexisting standards. The L7557 is suited for applications where a full loop range is needed, but low short-loop power is desired. It is a much lower-cost solution than a switching regulator, and also occupies much less PCB area, needing only a battery filter capacitor and a diode for implementation.