Just got 20,000 mike service and now there is a symbol displayed as a A with a line around it over the top of the A with an arrow head pointing down on the right. What is that mean?

The symbol you're describing is saying the salt tank is empty. Normally on this model if the dispenser isn't opening it's because it's not heating, the dispenser is triggered when it reaches a set temperature

Instructions

• 1 Press and hold down the lock button on the Firefly phone until the screen says "Enter Pin."
• 2 Press the "Enter" button to begin entering the PIN number.
• 3 Press the right arrow button once. You will see the number one.
  
• 4 Press "OK." You will see an asterisk on the top line.
• 5 Press the right arrow button twice until you see the number 2.
• 6 Press "OK." You'll see a second asterisk symbol on the top line.
• 7 Press the right arrow button three times until you see the number three.
• 8 Press "OK." You'll see a third asterisk symbol on the top line.
• 9 Press the right arrow button four times until you see the number four.
• 10 Press "OK." You'll see a fourth asterisk symbol on the top line. The phone will unlock.
• 
  Read more: http://www.ehow.com/how_6361971_unlock-firefly-cell-phone.html#ixzz309pjkqds

In guessing that since your lines have defaulted to pulse dialing that you have an older Nortel system such as an 8x24 or a 6x16 system. That being said you'll need to program touch tone dialing on each line.

Programming is done on M7310, M7324 and T7316 sets.
To set up ringing you need to enter programming by pressing the feature key followed by **266344.When prompted to enter the password enter 266344.
the display says A. Configuration
4 top line/feature keys are now used for programming
Press the show key (top right arrow)
the display will say1. trunk/line data
Press the show key (top right arrow) .
the display will say line 001. Press the show key (top right arrow)
the display trunk data press the show key (top right arrow) Press the next key 7 times(bottom right arrow) .
The display should say Dial mode: pulse.
Press the Change soft key (below the display). the display should now say tone. press the heading key (top left arrow) to get back to "trunk/line data" repeat the steps for the remainder of your active lines
press Rls when finished

it means low coolant

Programming is done on 7310, 7324 and 7316 type sets.
Enter programming by pressing the feature key followed by **266344.When prompted to enter the password enter 266344.
The screen should say TERMINALS&SETS. The 4 top line/feature keys are now used for programming.
Press the next key (bottom right arrow) .
The display should say Lines.
Press the show key (top right arrow)
The display should ask for a line number
Press the list soft key
The display should say Line001 and the line name. if this is the line name you want to change... Press the show key (top right arrow)
The display should say Name
Press the show key (top right arrow) .
Enter in the new name for the line
Press the next key (bottom right arrow) . If you want to program additional line names press the heading key(top left arrow) till you see "Line 001; new name" and press the next key (bottom right arrow) repeat the procedure for the additional lines
press the Rls key when finished

It's best if you use the "reply to post" window below the solution box so you can continue the same thread with the same person.

To set up the restriction filters we'll need to get into programming.
Programming is done on 7310, 7324 and 7316 type sets.
Enter programming by pressing the feature key followed by **266344.When prompted to enter the password enter 266344.
The screen should say TERMINALS&SETS. The 4 top line/feature keys are now used for programming.
At the terminals&sets prompt, press the next key (bottom right arrow).
The display should now LINES.
Press the show key (top right arrow)
The display should now ask for a line number.
Enter line number you want to change the line filter on. ex. 002 = line 2
Press the show key (top right arrow)
The display should say Trunk/Line data
Press the next key 2 times (bottom right arrow) .
The display should say Restrictions.
Press the show key (top right arrow)
The display should say Restriction Filters
Press the show key (top right arrow)
Enter in the restriction filter 25
Press the show key (top right arrow)
The display should say No Restrictions and the ADD soft key should appear on the lower right soft key
Press the add soft key and in the restrictions you want on the line.ex. 011any will bolck int'l dialing but not long distance. 0any and 1any will block long distance, operator assisted calls, and int'l dialing
You can also add overrides by pressing the show key (top right arrow) then the next key (bottom right arrow) .The display should say no over rides and the add soft key should appear on the right soft key.
When finished with the filter press the heading key(top left arrow)
The display should say Restriction Filters
Press the next key (bottom right arrow) .
The display should say Line restrictions
Press the show key (top right arrow)
The display should say Normal:none
Press the change key and enter 25.
Press the next key (bottom right arrow) .
Press the heading key (top left arrow) til the display says Lines.
Press the back key (bottom left arrow)
The display should say Terminals&Sets
Press the show key (top right arrow)
Enter in the extension number of the person you want to allow free use of the line.
Press the show key (top right arrow)
Press the next key 4 times(bottom right key)
The display should say Restrictions
Press the show key (top right arrow)
Press the next key 2 times(bottom right arrow)
The display should say Line/Set restrictions
Press the show key (top right arrow)
The display should ask for a line number.
Enter in the number of the line that was restricted.
Press the show key (top right arrow)
The display should say Normal: none
Change the filter to 00 (no restrictions)
That bypasses this extension from line filter 25
Press the next key (bottom right arrow) .
Press the release key when finished

Sets that are programmed to ring should automatically have ringing line preference.

Programming is done on M7310, M7324 and T7316 sets.
To set up ringing you need to enter programming by pressing the feature key followed by **266344.When prompted to enter the password enter 266344.
The screen should say TERMINALS&SETS.
The 4 top line/feature keys are now used for programming.
At the terminals&sets prompt, press the show key (top right arrow).
The display should now ask for an extension number. Enter extension number you wish to program ringing on.
Press the show key (top right arrow)
The display should sat LINE ACCESS
Press the show key (top right arrow) .
The display should say LINE ASSIGNMENT.
Press the show key (top right arrow) .
The display ask for a line number. press list
The display should say line 001: appear only
press the Chng key till it says appear & ring
press next key (lower right arrow)The display should say line 002: appear only
press the Chng key till it says appear & ring
repeat procedure for remailing active lines
press the heading key (top left arrow) til the screen says terminals&sets again

Prime line assignment is also programmed at the terminals&sets prompt.
press the show key (top right arrow). The display should now ask for an extension number. Enter extension number you want to change the prime line on.
Press the show key (top right arrow)
The display should say Line Access
Press the show key (top right arrow)
The display should say Line Assignment
Press the next key (bottom right arrow) .
The display should say Line Pool Access.
Press the next key (top right arrow)
The display should say Prime Line
Press the show key (top right arrow)
Press the Chng soft key till you get to the desired line or pool to pick up on
Press the release key when finished

The dead line needs to be taken out of the line pool soyou can grab the right line.First you need to know the line number that you need to take out of the pool.
thats done by entering feature *0 and pressing the line button for the dead line. the screen should say
L025: line 005 (the L025 is the important part).
Write it down for later.
Next you need to get into system programming.

Programming is done on M7310, M7324 and T7316 type sets.
Enter programming by pressing the feature key followed by **266344.When prompted to enter the password enter 266344.
The screen should say TERMINALS&SETS. The 4 top line/feature keys are now used for programming.
At the terminals&sets prompt, press the next key(bottom right arrow).
the display should say LINES
press the show key (top right arrow)
the display should ask for a line number (001-004, 025-028 *thats lines 5-8) enter line that you want to take out of the pool group and press show (top right arrow)
the display should say trunk/line use
press the show key (top right arrow)
display should say line type:pool A
press the change key until it says public
press the heading button(top left arrow) til it says lines again
repeat procedure for next line/lines
press the release key when finished
it grabs the right line.

Programming is done on 7310, 7324 and 7316 type sets.Enter programming by pressing the feature key followed by **266344.When prompted to enter the password enter 266344.
The screen should say TERMINALS&SETS. The 4 top line/feature keys are now used for programming.
At the terminals&sets prompt, press the show key (top right arrow). The display should now ask for an extension number. Enter extension number you want to change the pool on.
Press the show key (top right arrow)
The display should say Line Access
Press the show key (top right arrow)
The display should say Line Assignment
Press the next key (bottom right arrow) .
The display should say Line Pool Access.
Press the show key (top right arrow)
Press the next key till you get to the desired pool(bottom right arrow) .
Press the Chng soft key from N to Y
Press the heading key till the display says Line Pool Access(top left arrow).
Press the next key (bottom right arrow) .
The display should say Prime Line
Press the show key (top right arrow)
Press the Chng soft key till you get to the desired pool
Press the release key when finished

Programming is done on 7310, 7324 and 7316 type sets.
Enter programming by pressing the feature key followed by **266344.When prompted to enter the password enter 266344.
The screen should say TERMINALS&SETS. The 4 top line/feature keys are now used for programming.
At the terminals&sets prompt, press the next key(bottom right arrow).
the display should say LINES
press the show key (top right arrow)
the display should ask for a line number (001-004, 025-028 *thats lines 5-8) enter line that you want to take out of the pool group and press show (top right arrow)
the display should say trunk/line use
press the show key (top right arrow)
display should say line type:pool A
press the change key until it says public
press the heading button(top left arrow) til it says lines again
repeat procedure for next line/lines
press the release key when finished