In many telephones, the speaker phone may be off by default and is activated by pressing a button only when needed. This transmits the sound input and output from the handset to the loudspeaker and microphone , so that other persons can hear what is spoken and talk to the person or persons on phone.
There [...]
Earlier, speaker phones were usually used in companies where a number of people would participate in a discussion over the phone. The speaker phones would be much more expensive compared to conventional land line phones. However, with advances in technology, the price of speaker phones has reduced significantly. Also, many mobile phones are available with [...]