Liebert EM User Manual

The Liebert OpenComms™ EM is a compact, half-duplex device designed to monitor temperature, 

humidity, water detection and contact closure and notify personnel when those conditions exceed 

user-defined limits. 
The OpenComms EM is available in several models, which vary in size and number and types of 

ports. All models have sensor ports to monitor temperature, humidity, water detection and contact 

closure, and all models have either an external or built-in temperature/humidity sensor:

The OpenComms EM has sensor ports capable of monitoring temperature, humidity, water detection 

and contact closure through sensors that may be purchased separately (see Table 3). The unit’s auto-

sensing capability can determine which type of sensor is connected, making the unit ready to plug 

into your operation. Default settings for alarm limits may be changed through a Web interface.

The unit has an Ethernet port for connection to a network, which provides access to the Web interface 

and the capability of receiving alerts when monitored conditions reach alarm status. The 

OpenComms EM may also be configured to send e-mail alerts and SNMP traps over the network.

A modem port provides the capability of sending pager messages to notify personnel of alarm condi-

tions in the monitored area.

A Web interface makes it easy to view monitoring data in tabular and graphic formats, configure the 

device for alarm thresholds and set up automatic e-mail and pager notifications when a level in a 

monitored area crosses a predefined threshold.

EM PDU and vEM-14 controllers have two serial ports that are ideal for monitoring Liebert Managed 

Power (MP) Advanced Power Strips. Power, voltage, current and temperature levels can be monitored 

with user-configured alarm thresholds. In addition, some MP Advanced Power Strip models allow 

each receptacle on the power strip to be turned on or off through the Web interface.

An OpenComms EM is highly useful in monitoring:

• Enclosures, particularly those housing electronic equipment such as servers or telephone 

switching equipment sensitive to temperature, humidity and power fluctuations

• Process Areas, such as areas where environmentally sensitive chemical reactions occur
• A closet or an area of a room where temperature levels are important, for example, an area 

that houses many servers, where you want to verify the area or closet doesn’t get too hot

• EM

• has two sensor ports
• ships  with  an external sensor to detect temperature only (TMNET kit) or

both temperature and humidity (THCMNET kit)

• has no serial ports
• takes up zero U rack space

• EM PDU

• has two sensor ports
• ships  with  an external sensor to detect temperature only (TMPDUNET kit) or

both temperature and humidity (THCMPDUNET kit). 

• has two serial ports to monitor Liebert MP Advanced Power Strips
• takes up zero U rack space

• vEM-14

• has four sensor ports
• has a built-in temperature and humidity sensor
• has two serial ports to monitor Liebert MP Advanced Power Strips
• has 10 dry contact inputs 
• takes up 1U rack space