A lock indicator arm for a door having a latch mechanism includes a rod portion connectable on a first end to the latch mechanism, and a knob portion located on a second end of the rod portion opposite the first end and formed as a one-piece structure with the rod portion. This method includes; introducing a first essentially pure oxygen stream into a subterranean hydrocarbon-bearing formation traversed by at least one injection well and at least one production well, and initiating and sustaining in-situ combustion in the vicinity of the injection well. Several embodiments generate a test signal in response to coupling a device to a device interface, transmit the test signal on the bus, and generate an error signal when the bus signal at the device interface is different from the anticipated bus signal.