Se trata del "terminal maestro", es decir la "máquina" o "equipo" "maestro" que controla el resto de la maquinaria (las máquinas "esclavas" del terminal maestro, que hacen lo que este terminal les dicta...)

Oxford:
master
(Computing) (controlling device)
terminal (masculine) maestro
Example sentences
The main advantage of the cluster is that the computation power depends on the number of computers one adds to the master machine.
One device acts as a master and the devices connected to it act as slaves.
Whenever a machine becomes master, it takes over the virtual server address and continues with its original.

http://www.oxforddictionaries.com/translate/english-spanish/...

plant
2.2 uncountable (equipment)
maquinaria (feminine)
heavy plant (British English)
maquinaria (feminine) pesada

http://www.oxforddictionaries.com/translate/english-spanish/...

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Note added at 4 days (2015-12-23 07:03:07 GMT) Post-grading
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De nada, un placer ser de ayuda. :-)