Question about Panasonic Kx-Tgp600

You can extend the range with the Panasonic KX-A406CE.

Excerpt from the TGP600 brochure (bottom right): http://de.business.panasonic.ch/kommunikat...

KX-A406, 4-CHANNEL REPEATER
The range of the base station is about 300 m outdoors and 50 m indoors, depending on the environment.
If you need a longer range, the system can be optionally extended with the 4-channel repeater KX-A406,
which increases the communication range in practice to about 200 m indoors.
- Compatible with wideband audio
- Up to 3 units can be installed via cascade connection
- Up to 4 calls simultaneously
- Up to 6 repeaters per base station

Product page at the manufacturer: http://de.business.panasonic.ch/kommunikat...

This is exactly the configuration I have in use. Works perfectly!