What does the notation f(t)1(t) signify? I've come across this notation in a text on Control Theory, Modern Control Engineering by Katsuhiko Ogata, in a discussion of Laplace transforms. There is little more context I can give than that. The exact example involves the translation of function $f(t)1(t)$ to $f(t-a)1(t-a)$, so my guess was that it signified some sort of transformation, but I really have no clue. Google turned up nothing helpful, as did a search on this forum. Any ideas?

$1(t-t_0)$ is simply the step function, also denoted $u(t-t_0)$. $1(t)$ means $u(t-t_0)$ with $t_0=0$.

!Step function

Its value is $0$ before $t_0$, and $1$ after $t_0$. More info on Wikipedia.

The $1(t)$ is the unit step function and the $f(t)$ is just some other function and when multiplied they can represent some variable signal starting at time $t_0$.