There are several companies that market computer-based telephone systems that allow a recorded message to be delivered to hundreds or thousands of residents. These systems use a single recording and one or more out-bound telephone lines to make the calls.
One manufacturer offered the following chart to show how many calls could be delivered in different amounts of time. The chart assists an agency in determining how many out-bound telephone lines it needs to deliver how many calls in a certain period of time.
Minutes
1 5 10 15 20 25 30
-------------------------------------------------
4 / 4 20 40 60 80 100 120
8 / 8 40 80 120 160 200 240 [chart assumes each calls
12 / 12 60 120 180 240 300 360 takes one minute to complete]
16 / 16 80 160 240 320 400 480
L 20 / 20 100 200 300 400 500 600
I 24 / 24 120 240 360 480 600 720
N 28 / 28 140 280 420 560 700 840
E 32 / 32 160 320 480 640 800 960
S 36 / 36 180 360 540 720 900 1080
40 / 40 200 400 600 800 1000 1200
44 / 44 220 440 660 880 1100 1320
48 / 48 240 480 720 960 1200 1440
To determine lines needed: Determine the number of telephone calls that you need to make within a given period of time. For example, you have a call-out list of 65 persons for a HAZMAT incident, and you need to make the notification within 10 minutes. Go the 10 minutes at the top of the chart, then go down the column. You would find that 40 persons could be notified with four telephone lines, and 80 persons with eight lines. Then you would need about six telephone to make the required number of calls within 10 minutes. Use similar calculations for notifying entire neighborhoods or a group of businesses.