Or if they couldn't quite stretch to a phone, a pager clipped to their belt.
I remember a window of time in the early '90s where pagers were king, before the wider introduction of mobiles.
With hindsight, the ability for others to contact us at will accelerated exponentially in the '90s and into the '00s and beyond (BlackBerry / Nokia / iPhone tech, I'm looking at you). Work habits changed beyond recognition during this period of time.
It's probably one for another thread, but mobile tech really did change the landscape of working patterns. The last time I was uncontactable for work purposes was around 1999 before company work phones (Nokia in my example) became commonplace and with that came the expectation that one could always be reached if necessary. That said, I do remember journos that got called back to the office via. Pager from the early '90s.