User Guide
25
The pfl select lines are distributed along the same ribbon cable as the mix lines and enter
the module via ST2 pins 12 thro 19. These select lines are normally high [+15V]. They
are brought to 0V to enable the channel pfl output.
When enabled, the channel pfl output appears on the pfl mix buss via ST2 pin 10.
Switch LED powering.
The status LEDs are powered by the current source based around Q1. The order for
the chain starting from Q1 is main mute, meter changeover & matrix mute on the main
board. It then loops via ST6 pin 17 to the sub board. From here it goes to the matrix
on/off switches 1 thro 8. The chain finishes at the negative rail.