The Safety Controller monitors the mute devices to verify that their outputs turn ON within 3 seconds of each other. If the
inputs do not meet this simultaneity requirement, a mute condition cannot occur.
Several types and combinations of mute devices can be used, including, but not limited to photoelectric sensors, inductive
proximity sensors, limit switches, positive-driven safety switches, and whisker switches.
Corner Mirrors, Optical Safety Systems, and Muting
Mirrors are typically used with safety light screens and single-/multiple-beam safety systems to guard multiple sides of a
hazardous area. If the safety light screen is muted, the safeguarding function is suspended on all sides. It must not be
possible for an individual to enter the guarded area without being detected and a stop command issued to the machine
control. This supplemental safeguarding is normally provided by an additional device(s) that remains active while the
Primary Safeguard is muted. Therefore, mirrors are typically not allowed for muting applications.
Multiple Presence-Sensing Safety Devices
Muting multiple presence-sensing safety devices (PSSDs) or a PSSD with multiple sensing fields is not recommended
unless it is not possible for an individual to enter the guarded area without being detected and a stop command issued to
the machine control. As with the use of corner mirrors (see
Corner Mirrors, Optical Safety Systems, and Muting
on page
95 ), if multiple sensing fields are muted, the possibility exists that personnel could move through a muted area or access
point to enter the safeguarded area without being detected.
For example, in an entry/exit application where a pallet initiates the mute cycle by entering a cell, if both the entry and the
exit PSSDs are muted, it may be possible for an individual to access the guarded area through the “exit” of the cell. An
appropriate solution would be to mute the entry and the exit with separate safeguarding devices.
WARNING: Guarding Multiple Areas
Do not safeguard multiple areas with mirrors or multiple sensing fields, if personnel can enter the
hazardous area while the System is muted, and not be detected by supplemental safeguarding that will
issue a stop command to the machine.
Two-Hand Control Block
Default Nodes Additional Nodes Notes
TC
(up to 4 TC
nodes)
IN
MP1
ME
Two-Hand Control inputs must connect either directly to a Two-Hand Control Block or indirectly through a
Bypass Block connected to a Two-Hand Control Block. It is not possible to use a Two-Hand Control input
without a Two-Hand Control Block.
Use the IN node to connect input devices that must be on before the THC can turn the outputs on.
Either the TC1 input or the OS1 input has turn Off authority.
OS1 needs to be in the Run state before TC1 can turn the output of T1 & SO1 On.
Two-Hand Control
Function Block
M0:SO1
M0:TC1
M0:OS1
Figure 78. Timing Diagram—Two-Hand Control Block
XS/SC26-2 and SC10-2 Safety Controllers
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