Was there such technology in 1990?

[kenny1999]

I have just watched an old film produced in 1990. In the film, an undercover agent was given a small portable pocket button by the headquarter, it was claimed that whenever she pressed the button the headquarter would get the signal and found out where she was and would rescue her.

However, it was about an ordinary crime. Assume that it wasn't about military, was there such technology in early 1990 in reality? Generally speaking, how was the signal sent? By satellite? How far could it reach at that time? How precise was the location could it detect? I am not looking for very precise data, I am just asking out of curiosity.

[swansont]

Cell phones existed by 1990. GPS was fully operational in 1993 (though selective availability wasn’t turned off until 2000)

[CharonY]

39 minutes ago, kenny1999 said:

I have just watched an old film produced in 1990.

Excuse me, but old? What the heck, man? Totally uncalled for.

[studiot]

1 hour ago, kenny1999 said:

Generally speaking, how was the signal sent?

You said it yourself.

1 hour ago, kenny1999 said:

whenever she pressed the button the headquarter would get the signal

By pressing her button.

 

Transponders of one sort or another have been around for decades.

1 hour ago, kenny1999 said:

was there such technology in early 1990 in reality

They were certainly small enough by the mid 1970s to meet your description.