The good news is that all of you responding are young and have many long years of radio scanning ahead of you. The bad news is that "Still" and "Silent" alarms are ancient things, like me, and with respect to local application of these terms your responses were, sadly, not quite 100% correct.
First, for some reason, the fire service tends to cling to traditions for many different reasons. Long ago, fire chiefs rode in horse buggies to the fire scene. Those horses are long gone, the vehicle used by fire chiefs is still called "buggie" by some, as compared to the nature of the person within the vehicle.
Many years ago before most everyone having a landline telephone in their homes, there was a need to have a system to report fires. A medical doctor by the name of William Channing invented a system akin to the telegraph system, to summon the fire department. The rights to this were purchased by a guy name John Nelson Gamewell. Mr. Gamewell founded a company that manufactured these systems for many municipalities.
A fire alarm call box was located at a number of intersections throughout a city. Each box would have its own number. When someone wished to summon the fire department, (or others intent on being mischevious usually young miscreants such as me back in my younger days), they would go to the nearest fire alarm box and pull the red handle.
A signal would be sent from that box giving its number and was received at the fire department communications facility. Way back when, the Louisville facility was called the "Fire Tower", a term still used by some old timers. This signal would result in a series of bells being rung at the alarm facility. For example, box number 321 would have 3 rings, a pause; 2 rings and another pause; and 1 ring with a longer pause. This would be cycled a couple of times.
The folks at the fire alarm facility would look up the box number in their box cards index and determine which fire companies are to respond to that intersection.
The fire alarm operator would then set up another signal to go to fire stations over another telegraph type system. It would be pretty much the same thing a series of bells to indicate the box number.
Since numbers could be forgotten or confused, particularly if multiple alarms occurred at the same time, there was also a "ticker-tape" punching device that would punch a series of holes in ticker tape. This thing was called in Louisville "The Joker". There was a "Joker" at the fire alarm facility as well as at each fire station. The "Joker" was located at a certain point in the fire station and was called "The Joker Stand".
That term, means a place where communications occur between the fire station and the fire alarm facility, is still in use today. At our fire station, we have an area we call "The Joker stand", consisting of a blackboard, telephone, papers and a radio console.
Since there was no indication of what kind of fire was being reported, an alarm assignment, usually of three engines, two ladders (or trucks owing to where you are in the country) and one chief was sent to every incident reported by the fire alarm system.
As time marched on, more and more people started to have telephones. Since more information could be given on what exactly is on fire, the equipment to respond could be scaled back if needed.
Take the example of someone reporting by telephone a car fire. Usually only one engine would be sent. The fire alarm facility simply called the appropriate fire station on the telephone. No bells would be sent out, or ticker-tape punching. In other words, the "Joker was silent" for that call.
Another example would be an automobile accident with rescue being reported by telephone or perhaps police radio. In that case, one engine, one truck and one chief is the desired response. Again, the only communication would be a telephone call to the applicable fire stations. No bells and no ticker tape punching. Since that kind of alarm was a little different than the "Joker is silent" alarm, a different term was needed. So instead of the Joker being silent, the Joker was "Still".
As time marched along and radios became in use, there was an alerting signal sent out. Locally this consists of a single tone for a couple of seconds. This kind of alerting system came about when the space ace first came to be. So the term "Sputnik" was given to this single tone alerting fire people that a fire was about to be dispatched, and you should listen for whatever thing you need to listen to, in order to be informed of a fire to which you should respond.
If it was a serious fire, such as a building fire, you would hear the Joker going off for a Box Alarm. You checked your box cards to see if you were to respond.
A "medium" sized emergency, the Joker would be still, and your phone may ring, or you may have a radio go off.
A small sized emergency, the Joker would be silent, and your phone may ring or you may have a radio go off.
Years ago, they quit using fire alarm boxes at intersections and simply went to a telephone reporting system. All that equipment was removed and is now quite valuable to collectors.
The terms are still in use today in the interests of preserving heritage, traditions and so on.
A Silent alarm is usually a one company deal. A Still alarm is 2-3 companies. A Box alarm is more owing to where you are.
Today, we still use the "Sputnik" (and still call it "the Sputnik") tone on fire operations channels to alert firefighters that an incident is about to be dispatched, so you should listen to the radio dispatch channel.
This is but a small snippet of information concerning how the fire alarm telegraph system worked way back when. They have certain boxes to mean certain things, such as using a different channel, a firefighter fatality at a fire, multiple alarms, clearing alarms and so on.
Kind of fascinating and brings back many fond memories of visiting the fire alarm facility when they were doing this kind of system, back in the mid 70s.