• 802.11 b/g/n 150Mbps (130Mbps real)
  • wireless power output 20dBm – 100mW
  • MB flash memory (can be modified for 16MB)
  • 32 MB RAM (can be modified for 64MB)
  • USB 2.0 port (High-Speed, use hub for Low-Speed devices)
  • Powered via micro-USB socket
  • Tiny form factor: 5.7cm x 5.7cm x 1.8cm

Version Chaos Calmer 15.05 for ar71xx chipset can be used to flash the device version 1.6 or older, newer versions of openwrt and newer versions of the hardware (version 1.7) do not work without complexity.

The correct binary can be downloaded on a webpage or  local on this server.

On a MacBook you can run a webserver and wget the binary into the /tmp directory after telnet 192.168.1.1 or ssh into the device.
The latest version is  tl-wr703n-v1-squashfs-factory.bin
On the MacBook (first ifconfig): 

ifconfig eth0 192.168.1.5 netmask 255.255.255.0 up (modify eth0 if needed)
sudo apachectl start
sudo cp tl-wr703n-v1-squashfs-factory.bin /Library/WebServer/Documents/

On the WR703N:

telnet 192.168.1.1
wget http://192.168.1.5/tl-wr703n-v1-squashfs-factory.bin
sysupgrade -v /tmp/tl-wr703n-v1-squashfs-factory.bin

We found another useful page here and here