RA-25M Jumper Assignments:

Jumper Summary - 

JU1 - Remove this jumper to enable PTT LED false illumination 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 JU1 - but not required.  In the transistor position - select the position of JU1
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-35M 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-35M should fail.  JU1 controls the polarity of this 
function, explained below.

Jumper JU1 - False PTT LED illumination protection.
Jumper JU1 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 JU1 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, and transistor keying mode is 
selected.  This situation causes the red PTT LED to partially illuminate. This 
illumination can happen with just about any radio when the radio's power is turned off, 
falsely making it look like the radio is transmitting. Removing JU1 enables the BAT43 diode 
 / false illumination protection - in transistor keying mode. False PTT LED illumination doesn't
happen when relay PTT keying is selected at the PTT jumpers.

By default, we recommend NOT installing the JU1 unless the relay keying option is chosen,
then - JU1 should be installed.