Why don manufacturers just build power supplies into their cordless phones?
Most larger electronic devices have built-in power supplies: computers, TV’s, VCR’s, audio components, microwave ovens, etc. Smaller appliances, such as cordless phones don’t. The reason? First, put your fingers on a transformer plug when it’s in use. It’s warm to the touch because transformers generate heat. This is not a problem in the open air or with larger devices. However, if heat is trapped in a compact, light plastic device such as a cordless phone base, it will build up near delicate components and possibly cause damage. Second, transformers generate electrical interference, which may be significant if they’re in close proximity to a computer chip. Third, because the transformer is bulkier than any single component in a cordless phone base, it would change the design parameters for increasingly smaller and lighter phone devices. In a nutshell, it is easier and cheaper to design a lightweight cordless phone when an external power supply is used. Cordless power jack accommodates
