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=A1 is a so-called "plant designation" (IEC750), or "function oriented reference designation" (IEC1346). That is a function oriented designation, which is also denoted as “system” or “plant”. This designation is always marked with an equal sign. The IEC standard specifies that an equal sign should be used to mark the plant/function. Plant and function really means the same thing, namely a function oriented designation.
It is common practise to divide the plant designations in several sub-levels. This is also supported by the standard. These levels can be separated in three different ways:
1.This method implies that a dot should be used as separator character between the levels.
Example: =A1.B1.C5
2.More common, especially in recent years, is to repeat the equal sign to distinguish between the levels. This is the preferred method in most cases.
Example: =A1=B1=C5
3.A third method is available too, where no separator character at all is used between the levels. To keep the designation unambiguous, this method requires that all plant/function designations begin with letters and ends with digits. In that way, it is still possible to distinguish where one level begins and the other ends, without any separator characters. The risk of ambiguity often makes this a worse alternative than the two other ones.
Example: =A1B1C5
cadett ELSA supports all three methods. It is in fact also possible to use other separator characters than the ones allowed by IEC, but of course we recommend that you comply with current international standards.