The challenge of the project was to couple the central control devices (ZLG)
to the superordinate control stations (TLS-Nord, TLS-Süd and BSV).
	- The IEC 870-5-101 connection (1) will later be used to query diagnostic
	information or determine the switch authorization and it defines the switch
	authorization for TLS and BSV. 
- The IEC 870-5-104 connection (2) provides access to the ZLG. Both, the IEC 870-5-104
	transport layer and the IEC 870-5-101 application
	layer are used here.
- ipRoute passes the ASDUs (application layer) transparently to the ZLG.
	The link/transport layers between ipRoute and the relevant communication
	partner operate in in point-to-point mode. 
- Data flow towards HS Management is assigned to several RS232 connections
	as per the common address of the ASDU, to avoid bottleneck situations. 
- ipRoute can behave like a virtual RTU, i.e. the HS Management system can
	draw information on the state of the individual ZLG connections directly
	from ipRoute. 
- ipRoute configuration is limited to the transport paths. Individual
	information objects are not configured. 
- There is redundant coupling (3) between ipConv Nord and ipConv Süd. This
	connection determines which system is active and which is passive. The
	active/passive state is only relevant for the connection towards BSV and
	TLS, towards the substation, ipConv Nord and ipConv Süd receive data
	simultaneously. The physical link is realized with the Ethernet, connecting
	TLS Nord and TLS Süd. Both devices monitor each other by sending regular
	life signs to the remote partner (every second). If no life sign is received
	from the remote partner for a certain period (~5 seconds), it is considered
	down. If communication fails between ipConv Nord and ipConv Süd, both
	systems change to active state. 
- ZLGs are connected to the Ethernet via RS232/Ethernet converter ipEther
	232. Data is passed through transparently.
 
See also the follow-up project "BLS Lötschbergtunnel II"
Background of the Project 
 
Construction work on the Loetschberg tunnel (mountain line) first started in October 1906. In
1913, a 14.6 km long stretch between Kandersteg and Goppenstein was opened to
the public. 
At present, the new Loetschberg base tunnel is being built as part of the
NEAT initiative (New Railway Alp Crossing = Neue Eisenhahn-Alpentransversale). The Lötschberg base
tunnel, with its 34.6 km length, is one of the longest railway tunnels worldwide,
it connects Frutigen (canton of Berne, Switzerland) with Raron (canton of
Wallis). The tunnel enables a fast north - south traffic route, effecting
substantial expansion of capacity and choice.
The Loetschberg railway is to be operated by the BLS Loetschbergbahn AG (BLS =
Bern-Loetschberg-Simplon)
For further information please go to: http://www.bls.ch