Operation of the current limiter circuit
Note the red arrows I've added: -

Because there will be approximately one forward diode drop (0.6 to 0.8 volts) across R243, there has to be a current flowing through R243 that cannot exceed approximately 0.7 volts  ÷ 0.5 Ω = 1.4 amps. Hence the circuit current limits at about 1.4 amps.
The signal into R247 is used to turn off the pass transistor i.e. it acts like an enable input.