Off the hook

We have a 3 lane gate system, one for residents, one for visitor's and one exit. The resident lane has a sensor the the driver uses a "key card" to open the gate, there is also a "key pad" on a high post for school bus's UPS FedEx and so on who are issued a code to get in. The visitor lane has a phone number pad that the visitor dials the unit number, which calls the unit by phone and the unit resident dials "9" which opens the gate.

Here's our problem, often the phone pad is left "off the hook" and it sounds off the LOUD "off the hook signal" the same as if you left you home phone off the hook, the 'system' mistakes the loud off the hook sound for emergency traffic such as police/fire/ambulance and opens all the gates which stay open for a long time (I believe the system actually counts how many cars go through and closes after about 20 or more cars) which is unacceptable! In fact we believe many "regular visitors" with bad intentions know how to make the call system go to "off the hook".

The PM say's there is no way to fix this, but I dont believe this, there must be a way to adjust the call box to not mistake the off the hook alert for emergency vehicles.
We are tired of seeing dozens of cars just sailing through any of which could be armed with guns or drugs or both. Just the other day there was a shooting up the street from us.
Any thought's advice? Mostly if anyone knows the fix, is appreciated.
Don

Replace the “phone” device (assuming this is a microphone/speaker device a la wired telephone) with a push to talk box with a directional speaker. While this is a bit less private, it ensures there is no open comm circuit. It is also more sanitary.

What Cathy said!!! I haven't heard of that issue. The call boxes that I have encountered have pre programmed time out timers that automatically reset the call box after the call connects or there is a busy signal.