ComputerCraft 1.7.10 (v1.6.4) clock with redstone output

--This program can be used to create a digital clock on a monitor peripheral
--The monitor must be placed to the right of the computer

print("Running clock application. Hold ctrl + T to end.")
--peripheral.call("right", "setTextScale", 2)

local monitor = peripheral.wrap("right")
local sirenSide = "top"
local snooze = false

function wipeLine(y)
  monitor.setCursorPos(1,y)
  monitor.write("                      ")
end

function setSignal()
  monitor.write("   *ALARM*")
  if redstone.getOutput(sirenSide) then
    -- already set
    return
  else
    redstone.setOutput(sirenSide,true)
  end
end

function unsetSignal()
  if not redstone.getOutput(sirenSide) then
    -- already unset
    return
  else
    redstone.setOutput(sirenSide,false)
  end
end

while true do
    local decimalTime = os.time()
    local hours = math.floor(decimalTime)
    local minutes = math.floor((decimalTime - hours) * 100 * 0.6)

    local ampm
    if hours > 12 then
        hours = hours - 12
        ampm = "PM"
    else
        ampm = "AM"
    end
    monitor.clear()
    monitor.setCursorPos(1,1)
    if minutes < 10 then
        monitor.write(hours..":0"..minutes.." "..ampm)
    else
        monitor.write(hours..":"..minutes.." "..ampm)
    end
    sleep(.75)

    if decimalTime >= 18.541 or decimalTime <= 6.000 then
        setSignal()
    else
        unsetSignal()
    end
end