TBH GL 400 Manuel De Fonctionnement Et De Maintenance page 24

Electronic control and interface description
Functions:
infinitely adjustable speed controller
automatic readjustment of the airflow
optical advance warning at 75% filter saturation
optical display for filter blocked (shutdown of the device)
real time operating hour
display for notice of malfunction
switch and display for start/stand-by modus
Serial Interface functions:
serial interface: SUB-D
start/stop operation over interface
signal filter blocked
speed control over interface
notice of malfunction over interface
GL400-rev. 2.00 -24-
Technical changes reserved / Sous réserve de modifications techniques
Cambios técnicos reservados / Con riserva di modifiche tecniche
Technische Änderungen vorbehalten