PSR PAT ANTI-TWO-BLOCK Installation, Operator’s & Troubleshooting Manual page 8

PRE-OPERATION INSPECTION
2.
Anti-Two-block Alarm Light and Alarm Stop Button: The ALARM LIGHT BUTTON serves a
dual purpose. First, a red warning light illuminates when the anti-two-block limit switch contact
opens. This indicates that a two-blocking condition is approaching. At the same time, the BUZZER
(1) will sound and the following crane movements will be stopped concurrently: hoist up, telescope
out and boom down. (Whenever applicable) Second, it acts as an alarm stop button, which allows
the buzzer to be silenced temporarily.
3.
By-Pass Key Switch: The BY-PASS KEY SWITCH (3) can deactivate the cut off function of the
anti-two-block momentarily to allow the crane operator to override the control lever lockout. This
function can only be engaged by using the matching key. The BY-PASS SWITCH has 2 positions,
which are more specifically described as follows:

The neutral position is engaged when the plunger is out and the key can be removed, as
shown below. In this position, the by-pass key switch does not influence the anti-two-block
control lever lockout.

This position bypasses the anti-two-block control lever lockout. This function can only be
engaged by using the matching key. In this position, the cut off function of the system is
deactivated. To activate the switch, the key has to be turned clockwise for about 45 degrees
and plunger push in, then turned back to the middle position to lock it in place (as shown
below). After activating the by-pass key switch, the alarm light will constantly blink, indicating
that the cutoff function has been deactivated. During this operation, with the anti-two-block
switch activated, the alarm light will blink with a higher frequency. The BUZZER (1) for
approaching two-block conditions will be illuminated at all times.
Since this switch deactivates the cut-off function of the anti-two-block system, the
following instructions shall be adhered to:
The by-pass key shall be used with discretion, because unwarranted use to
override the control lever lockout system can result in harm to the crane
and endanger property and/or person.
Never use the by-pass key to either overload or operate the crane in a
range that is not permissible.
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