When should the Hi-Drive jumper be used on the pc board?
The modem ships with the little red jumper only on one of the pins at the small 2-position P1 pinheader in the upper corner of the modem pc board. In this “off” position, the Tx Audio signal generated by the modem goes through an internal 10K resistor, thus lowering the audio levels delieverd to the transmitter, making the drive level more appropriate for a transmitter’s “mic” input. Jumpering the two Hi-Driver pins with the little red jumper effectively removes the 10K resistor from the audio path, thus raising the driver level to “line” input levels (~1V RMS).
