RA-42M Jumper Assignments: Jumper Summary - JU1 - Selects the "Local Control" logic polarity. JU2 - Audio amplifier powering - select between USB 5V and a external 12V source. JU3 - Local Control or TX CTCSS select pin. JU4 - Remove this jumper to enable PTT LED false illimination protection. PTT - One of two jumpers to select transistor or relay PTT keying. See NOTE below. PTT - Two of two jumpers to select transistor or relay PTT keying. See NOTE below. NOTE: The PTT keying method is selectable by two mechanical jumpers. You choose between Transistor or Relay keying. The selection between transistor and relay keying is done with a pair of two - 2-pin headers in a square arrangement. These headers are red and require two jumpers to be placed in either a up/down or back/forth (vertical or horizontal) side-by-side orientation. Both jumpers are required for the option to work correctly. The up/down position selects the relay, while the back/forth position selects the transistor. These headers are located in a square box labeled "PTT" near the relay. If the relay position is selected - it's best to also place JU6 - but not required. In the transistor position - select the position of JU6 as required and detailed below. Local Control is a logic option that can enable a secondary control method. Some repeaters only require one logic lead change to enable internal controls. Not all repeaters have this control revert option, but for the ones that do, the RA-42 can feed such a line directly. This feature of enabling internal controls will allow the repeater to operate locally if the Asterisk application, computer, or RA-42 should fail. JU1 controls the polarity of this function, explained below. Jumper JU1 - Control Revert logic polarity. Position A = DB9 pin 7 Logic is high when COMM OK LED not lit. Position A = DB9 pin 7 Logic is low when COMM OK LED lit. Position B = DB9 pin 7 Logic is low when COMM OK LED not lit. Position B = DB9 pin 7 Logic is high when COMM OK LED lit. Jumper JU2 - Audio amplifier powering. Position A = Amplifiers powered from USB 5VDC. Suitable for many radio applications where the maximum required P-P voltage doesn't exceed 4 volts P-P. Position B = Amplifiers powered from external source 6 to 15 VDC. Some radios, like the Yaesu System Fusion, requires more than 4 volts P-P of audio. Many radios have a source of 10 to 15 volts readily available. Must be well filtered but regulation isn't necessary as long as enough current is available for the load. Driving speakers will require a power source capable of several hundred mA., depending on speaker impedance and desired listening level. Jumper JU3 - Local Control or TX CTCSS select pin. Position A puts the internal controls revert option to pin 7. Position B puts the TX CTCSS logic to pin 7. Since there aren't enough pins on the DB9 to bring the TX CTCSS function out to its own pin, it's routed to the DB9 (pin 7) as a jumper selectable option. If a user only wanted a LED as a status indicator, the jumper position is unimportant, as the yellow LED will illuminate no matter the position or existence of jumper JU3. Jumper JU4 - False PTT LED illumination protection. Jumper JU4 is removed to enable this illumination protection. The jumper can be placed if this option should it create a problem for a particular installation. The jumper simply shorts out the diode. Why is this protection and JU4 necessary? Partial (or full) illumination of the PTT LED can happen if the radio adapter is connected to a radio that has a PTT switching voltage (bias) of less than 5 volts. This is the case with many portable radios. This situation causes the red PTT LED to partially illuminate. This illumination can also happen with just about any radio when the radio's power is turned off, falsely making it look like the radio is transmitting. Placing JU4 disables the BAT43 diode protection. By default, we recommend NOT installing the JU4 unless the relay keying option is chosen, then - JU4 should be installed.