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GBM-8.2
tams elektronik
2. Operation overview
The GBM-8.2 track occupancy detector can monitor up to eight independent track sections. It
can be used in analogue and digital model railway layouts of all nominal sizes with a
maximum current consumption of 6 A per track section.
Adjustable sensitivity
The "correct" sensitivity at which a current consumer in a section is detected by the track
occupancy detector depends on several factors: If, for example, vehicles whose axles are
coated with resistive paint are to trigger an occupancy signal, a very high sensitivity is
required. In digital systems, however, high sensitivity can become a problem if interference
voltages from the digital system cause false alarms. Therefore, a lower sensitivity is usually
recommended for use in digital systems.
With the GBM-8.2, the sensitivity is adjusted separately for each track section at a trimmer
potentiometer and adapted to the individual requirements.
Evaluation of the busy signals
As soon as the GBM-8.2 detects a current consumer in a connected track section, the
corresponding output is internally connected to the output M. The output of the GBM-8.2 thus
acts like a switch that switches to ground. Digital feedback modules that switch to ground
(e.g. s88 feedback modules) can be connected directly to the outputs.
Display of the busy messages
To display the busy messages, LEDs (with suitable series resistors) can be connected to the
outputs of the GBM-8.2. Since the outputs of the GBM-8 can be loaded with a maximum of
50 mA each, they are not suitable for connecting incandescent lamps, relays or downstream
circuits with a higher current consumption. For these applications, the 4-fold track occupancy
detector GBM-1** is suitable.
Power supply
The GBM-8.2 is supplied with power directly via the rails. The track sections must be in one
booster circuit or supplied via a common driving transformer.
2.1. Use in analogue layouts
A typical application in analogue DC or AC systems is the use as part of a block position
control or an automated control system.
With the appropriate sensitivity setting, the GBM-8.2 detects vehicles with a current
consumption of at least 1 mA (e.g. illuminated locomotives or wagons) located in the
connected sections. Even the small current that flows in DC systems when an axle of a vehicle
is coated with resistive paint is sufficient to generate an occupancy signal when the sensitivity
is set to the lowest setting.
In principle, the GBM-8.2 can only detect vehicles in analogue DC systems that enter the
monitored track section from one direction of travel. Note: If the detection of vehicles from
both directions of travel is required, it is recommended to use a GBM-1** track occupancy
detector instead of a GBM-8.2.
6 | Operation overview
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