The early FM push-to-talk telephone systems were used in All Questions › Category: Embedded System › The early FM push-to-talk telephone systems were used in 0 Vote Up Vote Down Jayesh Bornare asked 3 years ago OPTIONS Simplex mode Half duplex mode Full duplex mode None of the above 1 Answers 0 Vote Up Vote Down Jayesh Bornare answered 3 years ago Half duplex mode