The L9217 requires a 5 V power supply and single battery to operate. This device offers forward and reverse battery operation. The rate of battery reversal may be ramped to meet international requirements. Additionally, a low-power scan mode, wherein all circuitry except the off-hook supervision is shut down to conserve power, is available. The dc current limit may be programmed via a single external resistor. Both the loop supervision and ring trip supervision functions are offered with usercontrolled thresholds via external resistors. Overhead is adequate for 3.14 dBm into 900 of on-hook transmission.