Music-On-Hold Box Music-On-Hold Box| DISCLAIMER: I\'ve collected these information from different sources. The author may revise this documentation from time to time without notice. THIS DOCUMENTATION IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. IN NO EVENT SHALL THE AUTOR BE LIABLE FOR INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES OF ANY KIND ARISING FROM ANY ERROR IN THIS DOCUMENTATION, INCLUDING WITHOUT LIMITATION ANY LOSS OR INTERRUPTION OF BUSINESS, PROFITS, USE, OR DATA. |
U1, an LS3404 melody chip is activated when "hold" S1 is pressed, which causes SCR1 to conduct and hold the telephone line via T1, R1, and LED1. The voltage across R1 and LED1 is used to activate the melody chip. Q1 and Q2 form a restart circuit to keep the melody chip going during hold.
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