Response in 12 hours
RFQ for SN7490Required Field
Output of 65-240 kHz crystal oscillator is divided by 1000 in three SN7490s to give 65-240 Hz tone required for access to amateur FM repeater. Choose crystal to give exactly desired frequency Q1 and Q2 are MPS6513, and Q3 is 2N1613. Supply can be 9 to 15 VDC from transceiver or from 9-V battery.-P. H. Wiese, Rock Solid Subaudible Tone Generator, 73 Magazine, April 1974, p 79-81.