The SI4438S4S-V1-C2A is an SMD type, RoHS compliant, radio frequency (RF) transceiver manufactured by Vollgo. The module is designed to transmit and receive data in the 433MHz frequency band and is available in either a 4mm x 2mm or 8mm x 8mm package size. It is capable of up to 250 mW output power and offers selectable data rates up to 500 kbps. The module also supports frequency hopping spread spectrum modulation, Manchester coding, 64-bit encryption, adjustable output power, sensitivity control, RSSI (Received Signal Strength Indicator) monitoring, and adjustable squelch threshold. Additionally, it is also designed for low power sleep mode for extended battery life and supports a wide supply voltage range (2.2-3.6V).