Not sure what signal your refering to...However:
1) The elevator phone must be ADA compliant..(whole nother set of rules there). The phone should self dial any in house or out of house connection that will be monatored 24 hours a day by a LIVE PERSON. The phone must play a recorded message, when the other end picks up, stating the location of the elevator. After the message is complete then the emergency operator can talk to the people in the elevator. Ususal response is "Opps..I pushed the wrong button". Once in a while there's actually somebody trapped. The elevator company usually has a monatoring service. We do not charge for this service for customers under contract. But we do charge for sending a tech out to extract the trapped...
2) Smoke detectors.. We're still arguing with the inspectors about this, but the smokes that set off the elevator on fire service must be limited to thoes in the elevator lobbys, hoistway and machine room. The elevator will react to only the 1st detector tripped and ignore all other detectors. The elevator controller is usually provided with a dry contact so that Simplex or whoever can wire it back to the main building alarm panels.
3) Shunt Trip Operation: Very badly written part of the code. Most locals havent adopted this part, but it calls for a heat sensor to be placed by each sprinkler head in the hoistway and machine room. In theroy the heat detector will cut off the power to the elevator before the sprinkler sprays water on the elevator equipment. Problem is then people are trapped in the elevator in the event of fire and usually end up roasted, smothered and wet. The State of Michigan adopted A17.1 -2000 but then recinded this section for obivous reasons.
Hope I've answered your question.. The best bet is to check with the elevator contractor and find out what applies in your area..
Word to the wise on new elevators..watch out for propritary equipment..or you'll be married forever...