Our 555 timer circuit
In our circuit, when the output is high, it turns on Q1, which turns on D2. When the output is low, it sinks the current, which turns off Q1 and turns on D1.
In our circuit, when the output is high, it turns on Q1, which turns on D2. When the output is low, it sinks the current, which turns off Q1 and turns on D1.