The Input Protection Module ( IPM ) relates to aprotection plug used in the telephone exchanges to protect the electronic exchanges from over voltage and over current. These plugs are used at the interface between the subscriber line and the exchange lines. This interface is called Main Distribution Frames (MDF).The protection of the electronic exchanges from over voltage and over current is ordinarily ensured by providing a GDT (Gas Discharge Tube) also called Arrester and a PTC thermistor.

The subject instrument is designed to test the important electrical characteristics of both the GDT and the PTC thermistor in an assembled state which is called the protection plug. Normally a protection plug comprises one three pole GDT and two PTC thermistors.

A GDT (Arrester) provides protection to personnel and equipment from abnormally high voltages which can be due to the result of lightning or electromagnetic induction.The surge limiting characteristics are designed to meet specific requirements. When the abnormal voltage reaches the specified level, a spark over occurs within the gas tube, and the surge is redirected to earth thus protecting the personnel and the equipment. It is thus necessary to ensure that the protection plug is built to meet various specified parameters to ensure that use of this component actually protects the personnel and equipment. The important parameter that need to be checked for compliance is spark over or strike over voltage.

PTC or Positive Temperature Coefficient Thermistor is an electronic device. This device ensures that current beyond specified value is prevented from flowing through it. This is achieved by the increase of resistance of the device which is proportional to the increase in temperature (Excess current raises the
temperature of the device). By limiting the current in this way, the Exchange Equipment is protected from External Overload and Short circuit. This makes the Exchange Equipment totally safe under all circumstances. The important parameter that need to be checked for compliance are resistance & tripping
& holding current characteristics of PTC.

1. Equipment                               : Combined GDT & PTC Tester
2. GDT Strike Range                    : 180V to 300V DC
3. PTC Range                                : 6 to 30 Ohms
4. PTC Hold Mode                        : 110 mA DC for 600 Sec
5. PTC Trip Mode                          : 250 mA DC for 90 Sec
6. PTC Rest Time                         : 300 Sec
7. PTC Restore Mode                  : 90 mA DC for 90 Sec
8. Display                                     : 20 Characters X 4 lines Alpha numeric back lite LCD
9. Indication (LED)                     : Pass , Fail, Power ON
10. Buzzer                                    :  Completion of Test cycle
11. Input keys                             : Six Keys
12. Accuracy                                : ± 2% + 1 Digit
13. External Connection            : By Terminals A, A1, B, B1,E
14. Input Power                          : 230V AC ± 10 %, 30VA
15. Input fuse                             : 250 mA 250VAC Fuse
16. Dimensions(HxWxD)          : 100x165x245 mm
17. Weight                                   : 2.725 kg