A support identification device comprising a support (BPA), e.g. a rack or backplane of a telecommunication system, and an identity receiver (PCB), e.g. a printed circuit board or card, coupled to an identity transmitter or connector of the support. The identity transmitter has several read pins (id1-id4=R1-R4) each at a logical level (0, 1) to indicate (identify) the type of support. The card (PCB) further has write terminals (W1, W2) coupled to dynamic terminals (D1, D2) of the support (BPA). These dynamic terminals are coupled to one or more of the read pins (id1-id4). The card is also provided with a program that sets the write terminals at a first logical level, reads a first logical level at each read pin (R1-R4), then sets the write terminals at a second logical level, reads a second logical level at each read pin, and determines from the difference between the first and the second read logical levels to which write terminal each read terminal is coupled, or not. This allows to obtain (2+w).sup.n identifications with n read pins and w write pins, instead of 2.sup.n+w identifications with the same total number n+w of read or basic pins.