Electrifier HC-05 Bluetooth Module 2 Pack Wireless Transmitter Receiver | Pair two units as master and slave via AT commands, push button on each board, 3.3V logic pins, integrated trace antennas

A single Bluetooth module connects a project to a phone. Two of them connect a project to itself — a robot to its controller, a rooftop sensor to a desk display, a moving vehicle to a stationary logger. The Electrifier HC-05 2 Pack exists for exactly that second category: builds where data has to travel between two of your own boards, and a trailing serial cable is not an option. Both units are identical, full-specification HC-05 modules on the ZS-040 breakout. The CSR BC417 chipset handles Bluetooth v2.0 with EDR on the 2.4GHz ISM band, with adaptive frequency hopping keeping the link stable and an integrated trace antenna keeping the footprint compact. Onboard regulation accepts 3.6V to 6V while every signal pin runs at 3.3V logic — direct wiring for 3.3V systems, one resistor divider on RXD for 5V boards. Pairing the two takes a single session: hold the push button on one unit to enter AT command mode, assign it the master role, and align the pairing code and baud rate (9600 by default, adjustable) across both. From that point they behave as a transparent serial bridge — whatever enters one TXD pin appears at the other RXD, no code changes required on either side. Since each module also works alone with a smartphone or PC, the second unit doubles as a spare or the seed of your next project. The pack suits robotics club builds, engineering coursework that requires both link endpoints, and telemetry setups across a workshop or home. Each unit carries its own one-year warranty from ISO-certified manufacturing, with the Electrifier brand assurance behind the pair.