If the machine has reversing capability where a hazard is possible during a muted condition, the control must include an
automatic means through which muting is permitted in the forward (non-hazardous) direction only. A Mute Enable signal
from the machine control, motor drive, or other machine logic, is a means to assist in meeting this requirement.
In muting applications involving an operator, all pass-through hazards must be eliminated so that the operator is continually
detected when in the defined area. This ensures that if a hazard arises, causing the mute cycle to end while the operator is
present, the safety light screen will immediately issue a stop. (See pass-through hazard information below.)
A pass-through hazard is associated with applications that allow personnel to pass through a safeguard, which removes or
stops the hazard(s), and then allows the individual to continue into the hazardous area. Subsequently the individual’s
presence is no longer detected, and the safeguard can not prevent the start or restart of the machine. A pass-through can
be created by as little as 75 mm (3 in) space between the defined area and machine frame. If the safety light screen is
muted while the individual passes through the defined area, a stop command will not be issued and the hazard cannot be
eliminated; the individual must be detected while entering the safeguarded area and the hazardous motion must stop
immediately. This is typically accomplished by supplemental safeguarding such as described in ANSI B11 standards or
other appropriate standards.
WARNING: User Responsibility
The user is responsible for ensuring that all local, state, and national laws, rules, codes, and regulations
relating to the use of this device in any particular application are satisfied. Make sure that all legal
requirements have been met and that all installation, operation, and maintenance instructions contained
in the device documentation are followed.
8.2 Mute Devices
The beginning and end of a mute cycle must be triggered by outputs from the muting devices, depending on the
application. The mute devices must either have normally open contacts, or have PNP outputs both of which fulfill the
muting device requirements (see
General Muting Device Requirements
(p. 60)). These contacts must close (conduct) when
the switch is actuated to initiate the mute, and must open (non-conducting) when the switch is not actuated and in a power-
OFF condition.
The EZ-SCREEN LPM monitors the mute devices to verify that their outputs turn ON within 3 seconds of each other (order
does not matter). If the inputs do not meet this simultaneity requirement, a mute condition can not occur.
Mute devices should be connected to the same power supply as the receiver. Several types and combinations of mute
devices can be used, including, but not limited to: limit switches, photoelectric sensors, positive-driven safety switches,
inductive proximity sensors, and “whisker” switches (see
General Muting Device Requirements
8.3 Mute Time Limit (Backdoor Timer)
The Mute Time Limit (Backdoor Timer) allows the user to select a maximum period of time that muting is allowed to occur.
The Mute Time Limit is either 60 seconds or infinite, depending on the mute configuration option selected (see Mute
Configuration Options table in
(p. 53)). The timer begins when the second muting device makes the
simultaneity requirement (within 3 seconds of the first device), and will allow a mute to continue for the predetermined time.
After the timer expires, the mute ends – no matter what the signals from the mute devices indicate. A Bypass (mute option
4) or Override (mute options 6 & 7) can be performed to clear the obstruction.
WARNING:
• Mute Time Limit
• Select an infinite time for the mute time limit (disabling) only if the possibility of an inappropriate
or unintended mute cycle is minimized, as determined and allowed by the machine’s risk
assessment. It is the user’s responsibility to ensure that this does not create a hazardous
situation.
8.4 General Muting Device Requirements
The muting devices (typically sensors or switches) must, at a minimum, comply with the following requirements:
1. There must be a minimum of two independent hard-wired muting devices.
2. The muting devices must either both have normally open contacts or PNP outputs both of which must fulfill the
input requirements listed in the Specifications. These contacts must close when the switch is actuated, and must
open (or not conduct) when the switch is not actuated or in a power OFF condition.
EZ-SCREEN Low-Profile System with Integral Muting
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