Low cost, compact electronic identifier apparatus interrogates a passive (no external power) or active (external power) transponder. Such identifier apparatus and transponder(s) may be used, e.g., for: (1) access control, (2) animal feeding and animal health, (3) inventory control, (4) process control, and/or (5) theft/security applications. The identifier apparatus further powers the transponder if it is passive. A power carrier signal broadcast by the identifier apparatus clocks and/or synchronizes the transponder operation. In response to being interrogated, the transponder sends back identification (ID) data. The ID data is received and extracted by the identifier apparatus in the presence of the power carrier "noise", and is then demodulated and decoded to recover the ID data. The electronic identifier apparatus uses a low cost, high speed, single chip microcontroller configured to operate so as to eliminate the use of decoders, drivers and other external circuitry.