13. GEARBOX AND GATE SAFETY
GROUP SAFETY GEARBOX (gears 1 -> 5)
This shift-down safety prevents shifting downinto the lower group (gears 1, 2, 3 and 4) once
the vehicle speed has exceeded approx. 30
km/h. The shift-down safety is installed on
vehicles with single H-type gearing.
In the case of an electrical malfunction (voltage
drop out), the safety is activated and the gears
1, 2, 3 and 4 cannot be re-engaged.
OPERATION
If the relay contact (G015) is closed, the supply
voltage will be applied to the group safety valve
(“single H” valve) (B079) through fuse E016. As
soon as the CTE-2 unit of the tachograph
receives a signal which corresponds to a vehicle
speed of less than 30 km/h, the CTE 2 will
switch the voltage to earth. As a result, the
group safety valve is activated and shifting down
into a lower group becomes possible.
If the vehicle speed exceeds 30 km/h, the
CTE-2 unit will break the earth connection and
shifting down is no longer possible.
GATE SAFETY (gears 4 -> 1)
If the relay contact (G015) is closed, the supply
voltage will be applied to the control switch
(E561) through fuse E016.
If the low group is activated, switch E561 is
closed and a voltage is applied to valve B293. A
supply voltage is applied to point 1 of electronic
unit D813 through fuse E019 and wire 1202.
Connection 3 of electronic unit D813 is
connected to the CTE-2. This is the
speed-dependent signal. Depending on the
speed, the electronic unit of the gearbox and
gate safety (D813) connects valve B293 to
earth. If both conditions are present, valve B293
is activated and the gate safety is active.
Shifting down from 3rd and 4th gear into the 1st
and 2nd gear is now impossible.
If the high group is activated, switch E561 is
opened and the voltage to valve B293 drops
out. At a speed in excess of approx. 12 km/h,
pin 4 of the electronic unit D813 is
uninterruptedly connected to earth. Shifting
down into 5th or 6th gear is possible, however.
SEE THE CTE SYSTEM MANUAL FOR MORE
INFORMATION
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