enable the system to function correctly. The system automatically chooses an available frequency during the linking process so that other DP trains nearby are unaffected. In a crowded yard or in hilly or mountainous terrain, it is not uncommon for the link to be temporarily lost. As long as there is not an emergency or penalty brake application that eliminates the link, the system will reconnect automatically or the operator can attempt to reconnect manually. Originally the loss of connection would result in the remote units remaining in their last-commanded throttle or dynamic braking position. Later system versions and software updates typically reduce the remote unit power setting to Notch 4 by default if the link is lost. Although the DP signals from lead to remote units (and vice versa) are nominally instantaneous, in reality it generally takes at least a few seconds for a remote unit to respond to a signal from the lead and for the change in status to show up on the DP display in the lead locomotive cab. Distributed power originally could be provided at only one intermediate location within a train. These forerunner systems (Locotrol 102-105 and Locotrol II) required a radio-relay car to be attached via standard MU jumper cabling to the remote locomotive(s) to provide the radio-control commands and to facilitate feedback signals. Later, Locotrol II evolved into the "Universal" system in which the radio-control equipment could be installed on the locomotives themselves. With this option, the relay car—variously referred-to as an RCU (remote control unit) or LRC (locomotive remote control)—was rendered redundant. Locotrol III was the next development, compatible with both the Knorr-Bremse/New York Air Brake CCB and Wabtec's EPIC electronic locomotive brake equipment, and permitting multiple remote unit locations. The latest incarnation of this equipment is LEB (Locotrol Electronic Brake), which integrates the GE Locotrol technology with K-B/NYAB's CCBII brake. Users Distributed power (as "Locotrol") is used in the United States, Canada, China, Australia (Queensland, the Pilbara region of Western Australia, and in the southwest of Western Australia), Brazil, Germany, Russia and South Africa. It is also (or has been) in regular unit-train operation in India, Mauritania, and Mexico, and almost made it into operation in both pre- and post-revolutionary Iran. In the south of Western Australia, Locotrol is used in the "top-and-tail" configuration rather than specifically for long-train operation. With the recent advent of electronically controlled pneumatic brakes (ECP)—either