Many integrated circuits have undocumented features or abilities. This is one of them. The TLC555 output (pin 3) can sink a 100mA load to 1.28V. The open drain transistor reset (pin 7) can sink 100mA ...

The Jackson Systems TK-400 is a universal twinning/paralleling kit designed to allow a single thermostat to control multiple HVAC units. It was engineered to incorporate solid-state, diode relay logic ...