Published:2009/7/11 2:12:00 Author:May | From:SeekIC
National LM3909 flasher IC is connected as tone oscillator that simultaneously drives loudspeakers at both sending and receiving ends of wire line used for Morsecode communication system. Single alkaline penlight cell lasts 3 months to 1 yeardepending on usage. Three-wire system using parallel telegraph keys eliminates need for send.receive switch. Tone frequency is about 400 Hz.- Linear Applications, Vol. 2, National Semiconductor, Santa Clara, CA, 1976, AN-154, p 5-6.
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