transmission distance;3-4km Size: 53mm*38mm*10mm wide interface:rs232,rs485,ttl frequency:433mhz,868mhz,915mhz and so on Product NameYS-C20K RF moduleSpecification1W RF module, 7.5V power supply, 433/868/915MhzBrief IntroductionRF output:1W Power supply: 7.5V Used name: YS-1020k Product Description 1.Products Main Features:* Carrier frequency: 433 MHz, 450MHz, 868MHz, 915MHz or ISM others;* ...