# What is the purpose of the two 1N4148 diodes used in this circuit?

What is the purpose of the two 1N4148 diodes used in this circuit?

Regards

Edit:Source page of the circuit..

When pin 3 of the timer is low, the voltage at the base of the transistor is about 1.4 V below Vcc, and therefore the voltage across the 180 $\Omega$ resistor is around 0.7 V. So the current through the transistor and LED's is about 3.9 mA, regardless of variations in supply voltage (which I guess is a 9 V battery, and can vary a lot). Hence the LED's should stay at the same brightness for a wide range of supply voltage.