blog:fire_alarms_over_voip
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| blog:fire_alarms_over_voip [2022/06/10 16:41] – created mike | blog:fire_alarms_over_voip [2022/06/10 16:42] (current) – mike | ||
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| The image below is an ancient clockwork "Morse code" style Grinnell fire alarm that predates common telephone use. These were wired in series, daisy chain style, and when the alarm went off it range the bells in different patterns. Firemen would look up the ring pattern (short, short, long, short... for example) to know where to go. The " | The image below is an ancient clockwork "Morse code" style Grinnell fire alarm that predates common telephone use. These were wired in series, daisy chain style, and when the alarm went off it range the bells in different patterns. Firemen would look up the ring pattern (short, short, long, short... for example) to know where to go. The " | ||
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blog/fire_alarms_over_voip.1654879260.txt.gz · Last modified: 2022/06/10 16:41 by mike