Do you need to get specific transformers-converters to run a cordless telephone and halogen lights from Europe?

Yes and no. European appliances run off 220V whereas American appliances run at 110V. However, American homes are wired for both 220 and 110 volts. 220 is just only used for large loads like ovens and dryers. If you know what you are doing you can install 220V outlets and then no, you don't need voltage converters. However, this is a very big job and is not worth the expense if you only have a few European appliances. You can buy 110-220V converters for this purpose.