Cell Phone Headset Interface, a Tool for Cutting PVC, and Covers for High-Voltage Connections

摘要

Cell phone headsets are very common and inexpensive. They usually consist of an earphone, an electret microphone element, and a two-circuit 2 1/2-milli-meter (3/(32)-inch) plug. This interface connects the cell phone headset to an Icom RJ45 jack and provides a push-to-talk (FIT) pushbutton switch. Provision is made for an external PTT connection for a foot pedal or similar. As shown in Figure 1, J1 is a 2 1/2-millimeter (3/(32)-inch) two-circuit jack for the headset. "Tip" is for the MIC, and "ring" is the earphone. The ring terminal is connected to the ring and tip of PI, a 3 1/2-millimeter (1/8-inch) two-circuit plug for the radio headphone jack. The tip terminal of J1 goes to the 2.2 kΩ resistor shunted by a 0.1 p.F capacitor, then to Pin 6 of the plug P2.