Without knowing the specifics of the console that was installed (I take it this is Arlington PD), your question cannot be answered as posed.
However, as a general matter, consoles that work 4-wire wireline channels can be programmed for either full duplex or simplex operation, where here the terms mean:
Duplex: the receiver audio on the input frequency remains on the "select" speaker even while the console operator is transmitting, albeit at a diminished level; and
Simplex: the receiver audio on the input frequency is muted while the console operator is transmitting.
With the consoles that I am most familiar with, this is as simple as setting Switch 8 ("FD") on the dual channel card to "on."