scope:

This European Telecommunication Standard (ETS) contains requirements for:

- the output performance of the direct current (dc) power equipment at the interface "A";

- the input of the telecommunications equipment connected to interface "A" powered by dc.

The dc voltage at interface "A" may be derived from the ac primary supply. The dc supply may incorporate a buffer battery.

This ETS also makes reference to safety and EMC standards which are in accordance with the relevant European standards.

This ETS aims at providing compatibility between the power supply equipment and the power consuming telecommunications equipment, and also between different system blocks connected to the same power supply.

NOTE 1: To ensure satisfactory performance, the connection of telecommunications equipment into installations is subject to the prevailing conditions of that installation and is subject to the agreement of both parties.

NOTE 2: This ETS is applicable only to -48 Vdc power supply interfaces. However, during a transitional period, other dc voltages may be used in existing installations. Annex A gives guidance on working in conjunction with existing -60 Vdc supply systems.

The power supply interface, interface "A" of figure 1, is a physical point to which all the requirements are related. This point is situated between the power supply system(s) and the power consuming telecommunications equipment.

NOTE 3: Interface "A" is located at the power terminals of the telecommunications equipment. Subject to the installation preconditions this point may be located at any other point between the power supply system and the telecommunications equipment by mutual agreement of the relevant parties.

The requirements at interface "A" apply to:

- the output of the power supply equipment or power supply installation of telecommunications centres;

- the power supply input of telecommunications equipment installed at telecommunication centres;

- telecommunications equipment, installed in customers premises, whose dc interface "A" is also used by equipment requiring a supply to this specification.

NOTE 4: Normally there is more than one load unit connected to interface "A". In these cases, interface "A" will undergo further restrictions with respect to noise limits or other disturbances specified in subclause 4.8.

NOTE 5: Disturbances on the power supply interface "A" relating to the continuous wave phenomena above 20 kHz is not covered within this ETS. ETS 300 386-1 [3] is applicable for this frequency range.

NOTE 6: The transients to which immunity is specified in this ETS are characterized by a high energy content such that electrical stress may be caused. Fast transients, the effects of which appear mainly as interference, are covered by ETS. ETS 300 386-1 [3] which details the electromagnetic compatibility of telecommunications equipment.

NOTE 7: An example of a configuration in which the interface "A" is identified is given in annex E.

The purpose of this ETS is:

- to use a power supply system with the same characteristics for all telecommunications equipment defined in the area of application;

- to facilitate interworking of different (types of) load units;

- to facilitate the standardization of telecommunications equipment;

- to facilitate the installation, operation and maintenance in the same network of equipment and telecommunications systems from different origins.