When were cordless phones first invented?

parent award to Nathan B. Stubblefield in May 12, 1908, details a "wireless telephone" able to transmit calls using radio. The large, if not entirely unwieldy transmitter does not looks too bad given the day. A further requirement for a series of wires suspended throughout the area, however, perhaps explains why it never caught on. From the Daily Telegraph...

One hundred years on, Stubblefield is finally being recognised as the inventor of the mobile phone. Just 30 years after the first proper long-distance phone network was set up, the Kentucky melon farmer was awarded the patent for his "wireless telephone".