# SMS, and the 160-character line

Study notes. Not vendor documentation and not legal advice.

- Wikipedia says SMS is a text messaging service that lets mobile phones exchange short text messages, typically over cellular networks.
- It says messages are up to 160 characters, originally for GSM, and that gateways can carry them through an SMSC.
- The article says MMS was later introduced as an upgrade with picture messaging.
- Sinch's SMS overview says you can send and receive SMS, including bulk SMS, and it names the Conversation API, the SMS REST API, and Enhanced SMPP.
- The Conversation API section says the same API can also send RCS, WhatsApp, Viber Business, and Facebook Messenger, and that hosting locations named there are US East and EU Ireland.

Write 160 as the Wikipedia maximum for a classic SMS, then write Sinch's channel list beside it. If the text is longer, write confirm for the segment count until you open the limit page the vendor cites.