SMS is the service through which text travels from one phone to another. Messages are limited to 160 characters including spaces, hence the name "short messaging service." Depending on your cell phone provider, your phone will either prevent you from typing past 160 characters, or it will send your message in blocks of 160 characters.
Short Message Service (SMS)
The Control Channel
Once your message is typed, it travels through radio waves to the control channel. The control channel is the pathway that allows your phone to communicate with your cell phone tower so that your phone can send and receive calls, data packets and SMS messages.
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The Short Message Service Center
The short message service center (SMSC) is the section of your wireless service that stores, forwards and receives SMS messages. Once a text message travels through the control channel, it arrives at the SMSC to be stored or sent immediately if the recipient's cell phone is active and enabled to receive text messages. If the recipient's cell phone is inactive or otherwise unable to receive text messages, then the SMSC stores the message until it can be sent.