An autonomous coverage robot system comprising: an active boundary responder (600,6012) comprising a wire (600,6012) powered with a modulated current placed along a perimeter (1006A,1006B) of a property; at least one passive boundary responder (600, 600A,600B,600C,600D,600E,600F,600G,600H,600I,6010,6010A,6010B,6010C) placed on a property interior (1001 A) circumscribed by the active boundary responder (600,6012); and an autonomous lawn care robot (10,11,12,13,14,15,16,17,18,19) comprising: a body; a drive system carried by the body and configured to maneuver the robot (10,11,12,13,14,15,16,17,18,19) across the property interior; and a boundary responder detection system (1500,1520) carried by the body and configured to detect both the active (600,6012) and passive (600,600A,600B,600C,600D,600E,600F,600G,600H,600I,6010,6010A,601 0B,6010C) boundary responders, the drive system configured to redirect the robot (10,11,12,13,14,15,16,17,18,19) both in response to the responder detection system (1500,1520) detecting an active boundary responder (600,6012) and in response to detecting a passive boundary responder, characterized in that: the autonomous lawn care robot further includes a signal emitter emitting a signal, the passive boundary responder is responsive to the signal, and the passive boundary responder is configured to signal the robot to maneuver over it and whether mowing should start, continue, or halt. an active boundary responder (600,6012) comprising a wire (600,6012) powered with a modulated current placed along a perimeter (1006A,1006B) of a property; at least one passive boundary responder (600, 600A,600B,600C,600D,600E,600F,600G,600H,600I,6010,6010A,6010B,6010C) placed on a property interior (1001 A) circumscribed by the active boundary responder (600,6012); and an autonomous lawn care robot (10,11,12,13,14,15,16,17,18,19) comprising: a body; a drive system carried by the body and configured to maneuver the robot (10,11,12,13,14,15,16,17,18,19) across the property interior; and a boundary responder detection system (1500,1520) carried by the body and configured to detect both the active (600,6012) and passive (600,600A,600B,600C,600D,600E,600F,600G,600H,600I,6010,6010A,601 0B,6010C) boundary responders, the drive system configured to redirect the robot (10,11,12,13,14,15,16,17,18,19) both in response to the responder detection system (1500,1520) detecting an active boundary responder (600,6012) and in response to detecting a passive boundary responder, a body; a drive system carried by the body and configured to maneuver the robot (10,11,12,13,14,15,16,17,18,19) across the property interior; and a boundary responder detection system (1500,1520) carried by the body and configured to detect both the active (600,6012) and passive (600,600A,600B,600C,600D,600E,600F,600G,600H,600I,6010,6010A,601 0B,6010C) boundary responders, the drive system configured to redirect the robot (10,11,12,13,14,15,16,17,18,19) both in response to the responder detection system (1500,1520) detecting an active boundary responder (600,6012) and in response to detecting a passive boundary responder, characterized in that: the autonomous lawn care robot further includes a signal emitter emitting a signal, the passive boundary responder is responsive to the signal, and the passive boundary responder is configured to signal the robot to maneuver over it and whether mowing should start, continue, or halt. the autonomous lawn care robot further includes a signal emitter emitting a signal, the passive boundary responder is responsive to the signal, and the passive boundary responder is configured to signal the robot to maneuver over it and whether mowing should start, continue, or halt.