Yesterday, I found a bridge under my bed, which I must have impulsively bought online but never got around to disassembling; I just opened it up to take a look at the structure. The internal circuitry is simple, but quite a bit of thought went into the structural design.1. Appearance
2. I was too lazy to remove the adhesive label, and as a result, I damaged the shell with brute force 
3. The structural part also shows a lot of thought, with the Zigbee antenna placed separately.
4. The module on the left is the Zigbee module; the one on the right is the Taiwan REALTEK RTL8196E, a 128-pin package, which integrates PHY, supports a single USB port, supports two 16550 UARTs, and supports up to 16 GPIO pins.
5. On the back of the board, the label shows that the Zigbee protocol is 3.0; I will open the module another day, but I won’t mess with it today.
6. The internal sides of the shell have slots, and the circuit board fits perfectly into the slots.