| 摘要 |
PURPOSE:To enable using either one of the stereo headphone with a three-pole sterio plug or the earphone with a two-pole monophonic plug by contriving a circuit through the use of a three-pole jack. CONSTITUTION:A headphone and earphone sharing circuit is provided with a shared jack 50 and a short-circuit preventing resistor R1. The shared jack 50 is provided with a negative pole side contact 52, a first positive pole side contact 54, the second positive side contact 56 and a contact piece 58 opening/ closing to the first positive side contact 54 by inserting/ejecting the plug. Then, the first positive side contact 54 of the jack 50 is connected to a voice output circuit and the second positive side contact 56 is connected to a DC cut-off capacitor 12 through the short-circuit preventing resistor R1. The contact piece 58 is connected to the incorporated speaker 14 of a communication equipment. Thus, eigher one of the three-pole stereo plug or the two-pole monopnonic plug can be used by one jack 50. |
