Before portable cellular phones, people like police officers or taxi drivers communicated from their cars using two-way radios. All of the radios in one city transmitted signals via a large, central antenna located on top of a tall building. With all callers sharing one antenna, the number of calls that could be made at any one time was very limited.
Consumers, like you and me, had an old type of cell phone that was permanently attached to the car and powered by its battery. The first transportable cellular phones had their own battery packs that allowed owners to detach them from the car and carry them in a pouch. However, most weighed about 5 pounds (2.25 kilograms) and were not very practical when used this way.