VoIP preserves tunnel communications

Edited by the Engineeringtalk editorial team Jul 7, 2008

The ES42H is an industrially hardened version of the standard ES42 Ethernet switch, constructed using a rugged metal case to deliver absolute reliability in demanding environments.

A sustained campaign across Europe over the last five years has driven tunnel safety to the top of the agenda as a key motoring issue, affecting not only personal safety but also countries' transport infrastructure.

Nowhere is this taken more seriously than in Italy, where on 24th March, 1999, a fire in the Mont Blanc tunnel linking Charmonix, France with Courmayeur, Italy, resulted in the deaths of 39 people.

Tunnels provide many of the primary links between Italy and France and Switzerland.

Fires can be lethal in road tunnels, where heat can build up extremely quickly.

The European Tunnels Assessment Programme (EuroTAP) was established to test tunnels across Europe and to make recommendations for safety systems and procedures.

Among the many measures identified by EuroTAP was the need for an effective network of emergency telephones throughout a tunnel, not only to provide fast warnings to emergency services in the event of a fire, but also to provide reliable communications points for the public when accidents or breakdowns occur.

The integrity of this SOS telephone system is paramount, since mobile telephones are unlikely to work deep in the heart of a tunnel.

The failings of conventional technologies were demonstrated last May in a 22-car pile-up in the Harvey Tunnel in New Orleans that saw 24 people injured.

None of the emergency telephones were found to be working.

In Italy, the Mont Blanc incident provided the stimulus for a series of research and development projects, aimed at optimising safety conditions in tunnels.

Recent years have seen a host of Italian companies and universities active in ITS research and development projects associated with tunnel safety, focusing on innovative components and integrated systems.

Much of this work is already coming to fruition in both new tunnel projects and in reconstruction projects on existing tunnels.

One example is the installation of a new VoIP (voice over internet protocol) emergency telephone network, installed by Italian system integrator Fort Fibre Ottiche, using VoIP phones from Teleindustria in conjunction with hardened Ethernet switches from GarrettCom Europe.

Teleindustria produces a wide range of emergency telephones, including models developed for use in tunnels.

This most recent project involved the company's VoIP telephones deployed along 3.2km of tunnel at 250m intervals.

Each telephone is connected to an associated GarrettCom ES42H Ethernet switch.

The ES42H is an industrially hardened version of the standard ES42 Ethernet switch, using high-grade components and constructed using a rugged metal case to deliver absolute reliability in the most demanding environments.

No airflow is required for cooling, allowing the switches to be constructed to be impervious to dust, dirt, moisture, smoke and insects.

The compact design provides six Ethernet ports, including up to two 100Mbyte fibre ports.

The fibre port choices cover all multimode and single-mode fibre connector types.

The ES42H models are suitable for operating directly off the mains power supply and provide the highest speed and bandwidth over single-mode network.

The switches are linked over fibre on twin ring networks, with the VoIP phones divided evenly over the two rings.

Both rings connect ultimately to a GarrettCom 6K8 managed Ethernet switch, which connects the VoIP phone network to an IP-PBX (internet protocol private branch exchange) and from there through a gateway to the normal public switched telephone network (PSTN).

The hardened switches ensure operational reliability and the ruggedness of the network itself is enhanced by GarrettCom's S-Ring technology, delivering high-speed fault detection and correction.

The S-Ring software runs on the 6K8 switch and monitors the ES42H switches on the two VoIP telephone rings, offering fast recovery in the event of a network break.

Should the ring be interrupted, S-Ring acts immediately to change the ring into two topological strings, ensuring that there is a path through the two strings for all normal data traffic.

Whil commonly used network recovery technologies offer recovery in around three seconds, S-Ring ensures network recovery in just 250ms.