... 20cm (write range is 70% of read range)Communication InterfaceWireless Bluetooth; Mini USBBluetooth Transmission Distance10-15mWorking voltageDC3.7-4.2V ( ... 40°C~+85°CAttachmentCharger,Data lines,SDKWe also can make bluetooth card reader to support 134.2K,125khz,13.56mhz ... with complete English SDK,demo software,source code and user manual,it can help you do application software developing,besides, ...