EMC for IT and office equipment

Information Technology and office equipment are primarily covered by the EMC standards EN55022 (EMC emissions) and EN55024 (EMC Immunity).

These standards are applicable to information technology equipment (ITE) which has a primary function of either (or a combination of) entry, storage, display, retrieval, transmission, processing, switching, or control, of data and of telecommunication messages and which may be equipped with one or more terminal ports typically operated for information transfer.

These standards specify various emissions and immunity test to be carried out on the product either through radiated means or by conduction along the signal or power supply cables.  In particular, emissions and immunity tests are required on telecommunications or network ports (e.g. Ethernet, ISDN, PSTN or similar).

EN55024 also gives specific requirements and performance criteria for different ITE types; these are divided up in to 7 categories within the Annex’s.  It should be noted that multifunction equipment may fall into the requirements of more than one annex:

• Telecommunications terminal equipment (TTE)
• Data processing, display, input, printing or processing equipment
• Local area networks (LAN)
• Printers
• Copying machines
• Automatic teller machines (ATM)
• Point of sale terminals (POST)

The test requirements of these standards include conducted RF emissions, radiated emissions, radiated immunity, conducted RF and transient type immunity tests on power and signal cables as well as ESD (Electrostatic Discharge).

Work is currently in hand preparing a new series of standards CISPR 32 (EMC emissions) and CISPR 35 (EMC immunity) that will cover 'multi-media equipment (MME)' This new set of standards will replace the existing ones (CISPR 22 and 24)

When CISPR standards are published as International standards they are normally transposed into European standards without modification and given a new number whilst keeping the orignal international reference. For example CISPR 22 becomes EN55022.