You can notify other users in a channel you are in of your desire for them to read your message by using a Mention. You can take advantage of Mentions by typing an ‘@’ symbol in your message body. Once you type ‘@’ an option list will pop-up above your text entry field. This will give you options like ‘@Admins’ or ‘@Channel’ (Which will alert channel administrators or Everyone in the channel respectively). Select them using your arrow keys on your keyboard, by clicking the option you want using your computer mouse, or by touching the option on a touchscreen device.
If you would rather send a message to a specific individual or individuals, you can do so by continuing to type after the ‘@’ symbol. For example, if I wanted to get the attention of ‘BettyWhite’ in the GoldenGirls channel, I would navigate to the channel, begin typing ‘@’, then without spaces start typing ‘Betty’ (it would look like @Betty). The field above the text entry line will adjust to show you the best matching username as you type it. Once you see ‘BettyWhite’ appear, you can select it in the same way explained above. You can repeat this step if you wish to include other members of the channel in your mention.
Once you’ve added your mention, finish your message and send it. The user included as a mention in your message will receive a floating notification in the Semaphor application that there is a message awaiting their attention. If you have a mention you have not seen yet, you will see a solid red circle next to the channel you were messaged in.