frequently asked questions

frequently asked questions
Integrated Protection Module (IPM)
Date: 8th April 2015
Version: V1R1
Author: Tapan Upmanyu
How Integrated Protection Module (IPM) safeguards your PBX?
Analog trunks (commonly known as CO/FXO/TWT) and analog extensions
(commonly known as FXS/SLT) are widely used in telecom world. These trunk
lines and cables connecting an analog phone to the PBX are generally two wire
metal cables, which run over large distances covering different terrains and
environments. Hence such cables exhibit vulnerability of coming in contact with
power cables and lightning. Such situations will lead to passing of high
voltage/current in the cables which may ultimately damage the terminal
equipment. Further user will have to invest in repairing of the damaged PBX.
Below given photograph shows a card damaged due to lightning/surge.
To prevent such failure, it is advisable to install surge and lightning protectors.
One of such device which can help to reduce the risk of damage due to the surge
or lightening is IPM (Integrated Protection Module), also known as Subscriber Line
Protector. IPM is inserted in the Krone module in the Main Distribution Frame
What is IPM made up of?
IPM is made up of GDT (Gas Discharge Tube) and PTC (Positive Temperature
Coefficient) Resistors.
PTC (Positive Temperature Coefficient)
Resistor for Over Current Protection.
GDT(Gas Discharge
Voltage Protection.
How to install IPM?
 The below given procedure must be followed to install IPM in MDF
1. The MDF box is provided with a grounded metal strip to which ground pin
of IPM is connected.
Metal strips (connected to ground), to which IPM’s
ground pin will be connected
The MDF box along with metal strips is
commonly grounded using a ground wire
2. Insert the IPM in the Krone Module.
3. It is mandatory to ground the IPM from its ground pin using a metal strip in
the MDF as indicated earlier.
These pins will be in contact with
the grounded metal strip in the MDF
How IPM safeguards your PBX?
There are two cases possible when IPM serves as a protection:
 Over Voltage Protection:
High voltage comes
on the line
GDT gets into ON
mode and prevents
the voltage to enter
the PBX
GDT gets back to
OFF mode when
voltage on the line
gets reduced
 Over Current Protection:
High amount of
current comes on
the line
PTC resistors get
their contacts open
and break the circuit
After the current
reduces on the line,
we have to replace
the IPM with a new
How to verify if the IPM is working or not?
a. How to verify if the Positive Temperature Coefficient (PTC) Resistor in the
IPM is working perfect or not?
Once the PTC gets faulty you will not get dial tone on the port connected to the
line because there will not be any connectivity between System & Field Cabling
By following these steps it can be identified that PTC is working or not.
 Remove the IPM from the krone module and check if there is any dirt
accumulated on the connectors. If yes, remove the dirt
 Check for the continuity between the Tip and Ring on the input side and Tip
and Ring on the output side
Tip and Ring on output side
Tip and Ring on input side
 If continuity is there, insert the IPM back into the Krone module else replace
it with a new one
b. How to verify if the Gas Discharge Tube (GDT) in the IPM is working perfect
or not?
 Certain third party equipments are available in the market to check if the
GDT in IPM is working perfect or not. It is advisable that IPMs are periodically
checked using such equipments.
 It is mandatory that, the MDF box must always be equipped with IPMs.
Removing IPM does not ensure that your circuit is safe from surge. After
removal of IPM the system does not become an open circuit and it is not safe
from surge.
It is better to install IPMs and prevent your system from surge, then repairing it
later on, which leads to loss of time and money.
For more information, contact
Matrix Technical Training Team
[email protected]
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