You need to use actions with Output (CO) objects.
Configure an action on the sensor to turn the CO on (sensor properties, general, Actions - change the CO state to 'on').
You then configure an action on the CO to do the change you want ( see example below)

This way as soon as the sensor is triggered the Output turns on and stays on, you then have another action on a different sensor to turn the Output off again (to reset it).

You can't use the sensors directly with doing the change because the sensors flicker like crazy and don't stay on, so the change you want to action gets spammed like crazy because it constantly goes on and off.


Example: This Action configured on the CO will set the train currently allocated in block 92 to change speed to cruise and turn the sound on 3 seconds after triggered.
I use this when a train triggers a sensor near the exit of a tunnel from the staging yard, reduces speed from Max to Cruise and then turns the sound on.

<?xml version="1.0" encoding="UTF-8"?>
<xmlscript>
<query vr="lcid92" table="bklist" id="92" get="locid"/>
<lc id="@lcid92" V_hint="cruise"/>
<sleep time="3000"/>
<fn id="@lcid92" fndesc="Sound" fncmd="on"/>
</xmlscript>

Please note that the block does not trigger the event at all but the system uses the trains last location (block 92) to determine which train to apply the changes to.
This works not only for occupied blocks but also reserved or departing or crossing.