Honda key fob inside case
Main internal components
Printed Circuit Board (PCB) — The green (or sometimes black) electronics board that holds almost everything. It contains:
A small microcontroller
RF transmitter circuitry (usually 315 MHz or 433 MHz)
Antenna traces or a small antenna component
Contact pads for the buttons
Battery contacts (metal spring clips or prongs)
Coin-cell battery — Almost always a 3-volt lithium coin cell:
Newer smart-entry fobs → usually CR2032
Older or smaller remotes → often CR1616, CR1620, or CR2025
The battery sits in a molded cradle and is held by metal contacts. Polarity matters (usually + side facing a specific direction).