• Modular system design: Arrangement of the components between main station and end unit in any order
• Lightweight, but sturdy components such as speaking stations, signal buttons
• Four-wire system line
• Rugged, reliable connection technology
• Connection of signal and supply voltage independent of polarity
• Supply voltage indicator light at each speaking station
• High volume and good intelligibility of the loudspeakers
• Signal and central unit call button at each speaking station
• Possibility of connection to other WL systems or WL 200 intercom central units

The intrinsically safe L111 loudspeaker system is used for clearly audible communication and signalling in coal mines, e.g. for:

• belt conveyors
• monorails
• ropeways
• rope-drawn floor rail systems

The L111 system is a low-cost loudspeaker system. It is designed with "intrinsic safety EEx ib I" protection and is approved (BVS 96.D.1128X, marking SYST EEx ib I).

The system components, which must remain in operation for communication purposes after the power supply is disconnected as a result of an increase in the methane content, conform to type of protection EEx ia I.

The intrinsically safe L111 loudspeaker system is of linear construction, the individual system components being connected to each other via the 4-wire system line (e.g. L2YY(Q)Y 2 x 2 x 1.5).

The L11-H2 main station is the starting point of the system line and supplies all equipment connected to this line with current from the power pack connected to the L11-H2 main station. The lines for control of the start-up warning and the lines for coupling the L111 system to a WL200 switching system or other WL systems to form a communication system with sectional start-up warning are likewise connected in the L11-H2 main station.

The L11-H2 main station monitors the WL lines for breaks and produces the required audible signals for "WL line faulty" and "start-up warning", which are transmitted via the system cable to the speaking stations and emitted by the latter with a high volume.

The L11-E2 end unit forms the termination of the system line.

The following equipment can be looped in between the L11-H2 main station and the L11-E2 end unit in any order:

• LV30 speaking stations with two loudspeakers
• LST12 signal buttons for transmission of the signal tone (1980 Hz/-6 db)

The number of units, which can be looped into the system line within a supply section is limited to a maximum of 40 LV30 and/or LST12, a maximum of 6 supply sections being permissible. The DC wires of the system line between the supply sections must not be connected through.

The maximum length of the system line of a supply section is achieved, if the supply voltage at the end is 8 V or less and depends to a large extent on the number of built-in units, because these are supplied via the system line.

Each speaking station has a built-in storage battery, which is charged continuously via the system line. This storage battery enables firstly a high volume with low current withdrawal from the system line and, secondly, temporary emergency operation of the L111 system in the event of a power failure or disconnection from the supply. If the supply voltage is switched off as a result of an increase in the methane content, all speaking stations remain ready for operation thanks to their built-in ia-certified storage battery

Plug-in LV30 speaking stations, L11-E2 end unit and system lines (6-pole plug-in connector), hence:

• simple and rapid assembly of the system lines
• short stoppage times due to rapid changing of equipment.

The L11-H2 main station is equipped both for permanent and plug-in connection of the system line.