Signal operated tools for milling, drilling, and/or fishing operations

SIGNAL OPERATED TOOLS FOR MILLING, DRILLING, AND/OR FISHING OPERATIONS A jar (600) for use in a wellbore, comprising: a tubular housing (610) having a lower end for connection to a downhole tool; a tubular mandrel (605) having an upper end for connection to a workstring and a lower end extending into the housing (610); an anvil (610a) formed in the housing (610); a hammer (607) connected to mandrel (605); a valve (625) for accumulating fluid pressure in the jar (600) in a closed position and for releasing the accumulated fluid pressure in an open position, thereby causing the hammer (607) to strike the anvil (610a); and an electronic actuator (653), comprising: a battery (314); a receiver (302) operable to receive an instruction signal; and a controller operable to selectively lock the jar (600) and to release the jar (600) in response to receipt of the instruction signal, wherein the receiver (302) comprises an antenna (302) located adjacent to a flow bore of the jar and operable to receive the instruction signal from a radio frequency identification (RFID) tag travelling through the flow bore.