What exactly is an terminal adapter (TA) in an mobile station? Why a terminal equipment (TE) and an mobile termination (MT) can't communicate directly via AT protocol? Why it needs this separate adapter device between them?

And why an termination adapter is mandatory on UMTS/3G but not on GSM?Wikipedia

I can't find any accurate resources about this from Internet :(

1 Answer 1


Think of a modem - an adapter between an analog line (POTS) and a computer.

A terminal adapter is an adapter between a digital line (ISDN, GSM, LTE, ...) and a computer. It's not a MOdulator/DEModulator since data doesn't need to be modulated onto a digital line. A terminal adapter is required when the line termination has no direct interface for a computer.

  • The question is about an terminal adapter in GSM context (and 2nd question about UMTS). I understand that a terminal equipment (e.g. conputer itself) can't directly communicate with GSM and for that it need an mobile termination, thats clear. But for what we need 3rd device? That's the question, can you explain this? Another question is, why an terminal adapter is mandatory on UMTS but not on GSM. P.S. Sorry for poorly detailed question.
    – worner
    Dec 4, 2023 at 18:12
  • There's no general difference between attaching to GSM, UMTS or LTE. The wording in Wikipedia indicates that 2G/GSM equipment doesn't necessarily have to provide terminal-adapter functionality while 3G/UMTS and faster does.
    – Zac67
    Dec 4, 2023 at 19:26
  • Wikipedia says just "In 2G (such as GSM or CDMA), the terminal adapter is a theoretically optional while in 3G (such as W-CDMA), the terminal adapter is mandatory and is part of the mobile termination." and that doesn't tell anyr eason for that. Do you know what in UMTS needs terminal adapter as mandatory?
    – worner
    Dec 5, 2023 at 1:21
  • And still main question is, what exactly is terminal adapter? E.g. something circuit between MT and TE or just another name for the interface that them both implements(AT)? Please expand your answer post.
    – worner
    Dec 5, 2023 at 1:23

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.