Like some previous reviewers I already had a Gigaset SL400A system Gigaset SL400A Twin DECT Bluetooth Cordless Phone - Black / Silver
with two handsets which I have been really pleased with. I Then decided to extend it by adding a third handset in another room.
I expected this phone to be less busy than the others so decided to economise a bit by getting the less capable (and significantly less expensive) C300H, recognizing that not every feature of the SL400 would be supported. The Gigaset website has a handy compatibility tool which shows the extent of compatibility between the many available base units and handsets.
The main areas of SL400 inter-operation which are not supported that I have noticed in practice are:
The C300H does not recognise the SL400A answering machine so cannot play messages or use other answering machine functions.
Outgoing calls made from the C300H are not logged in the SL400 call lists. The C300H does keep a Redial list of called numbers though.
The C300H does not display the 'name' of the other (SL400) handsets when pressing 'INT' on the control key. However it is aware of the other handsets, so they can referred to by their number when calling internally or transferring calls. Thus, press 'INT' on the control key then 1 to call the INT1 handset. SL400 handsets recognise and display the C300H as 'INT3' in my case.
To me, these are minor limitations and I am very pleased with this phone. Making and receiving calls is easy and call volume and clarity is great. Phone numbers can be transferred to and from the SL400 directories without problems. The C300H phone may not have all the tricks but it looks businesslike and does what it does well. Great value.