Pagers were small devices that you usually clip on a waistband of slacks / pants, or attach to the outside of a woman's purse, so you could easily check the message. They were the predecessor to cell phones, but there was a lap over, at least by some major companies, requiring some employees to carry both pagers and cell phones.

The pager that I carried could accept either phone numbers or actual text messages. I had to carry a pager as well as my cell phone, to make sure anyone could reach me, 24/7.

https://en.wikipedia.org/wiki/Pager