ITU-T K.17 1988 Edition, November 1, 1988
Tests on Power-Fed Repeaters Using Solid-State Devices in Order to Check the Arrangements for Protection from External Interference
Additional Comments: W/D NO S/S
Published By:International Telecommunications Union -Telecommunication Standardization Sector (ITU-T)
As pointed out in Recommendation K.15, § 4.1, it is advisable that the test conditions simulate real conditions as closely as possible. As certain Administrations may be exposed to different environments, or have different service objectives or economic constraints, these tests may be modified to adapt them to conditions.
If the environment is not known, the text given in this Recommendation should be applied.
None of the tests given in this Recommendation should cause any significant change in the in the characteristics concerning the repeaters under test.
In particular, this applies for:
a) current and voltage in the feeding circuit,
b) gain-frequency characteristic,
c) total noise,
d) bit error rate.
The tests consist of:
- prototype tests,
- acceptance tests.
Tests are intended to check the effectiveness of all the various arrangements made to protect repeaters using solid-state devices. These arrangements include protective devices incorporated as an integral part of the repeater or installed externally at the repeater location.
Prototype tests are carried out to check the effectiveness of the repeater design and protective elements in a severe environment.
In deciding what protective measures should be adopted, allowance should be made for the most dangerous e.m.f.s that may be produced at the inputs and outputs of repeaters using solid-state devices, even where the occurrence of such e.m.f.s is very rare.
When a repeater using solid-state devices with lightning protectors at its input (or output) terminals is subjected to an impulse voltage, the (residual) energy capable of reaching components within the time-interval from zero to an impulse voltage, the (residual) energy capable of reaching components within the time-interval from zero to the striking-time of the lightning protectors depends, among other things, on the steepness of the impulse wave-front.
During the prototype test this residual energy should be as large as in the worst case that may be expected in practice.
This is ensured by choosing an impulse wave of suitable steepness and amplitude. It is, however, additional to the test described previously, which recommends that the repeater be subjected to an impulse having an amplitude less than the striking voltage of the lightning protectors, in order to find out how it responds over the whole of the impulse wave.
These tests are carried out on equipment after assembly, to check that the protection is working properly. The test is in general less severe than the prototype test in order to avoid exposing certain components to a degradation that might remain undetected by any measuring process. However, users are at liberty to stipulate more stringent tests (adapted to special, real conditions).
The user may decide whether the tests are to be carried out on each equipment or by sampling.
Note – In certain circumstances, users may consider it worthwhile to carry out additional tests adapted to their own special requirements. Such tests are not given below.