Can someone explain business frequencies.. Trunking.

Can someone explain what type of system KD45157 is? I do not understand what it all means.. Monsanto for instance, Why does it have 4 different call signs for the same factory. I understand having different frequencies, but shouldn't there be a control frequency because it is trunked?



eg. WQIP865 has 5 different frequencies

WPGV227 has 2

KD45157 has like 10



But it is the same factory. Why have 3 different call signs? What is the control channel. Thank you.

Can someone explain business frequencies.. Trunking.