The triple pressure indicator has three dials on its front face. The top gage shows the system hydraulic pressure available (Yellow hydraulic system or accumulator) the bottom two gages show the hydraulic pressures:
- that go to the left MLG brakes
- that go to the right MLG brakes.
With Anti-skid turned on and park brake not set you'll be using normal braking hence no indication. Turn off the Anti-skid/NWS switch and you'll use altn braking and hence indication will show. Accumulator pressure is used for park brake so this is also indicated.