Here's a "circuit golf" challenge (the goal is to solve the problem in minimum cost/complexity without using specialised components.
The "HomeBus" communication standard (which Mitsubishi calls M-Net and some others refer to as P1P2) sends 9600 baud RS232 bytes using inverted "alternate mark inversion" (successive zero bits are sent 2V pulses with alternating phases) on a 12-15V multi-drop wire pair of indeterminate connection polarity.
Your goal is to detect both +ve and -ve pulses, and stretch them both to
100us +ve pulses so they can be fed into a UART to make a HomeBus receiver. There are chips to do this, e.g. MM1192/XL1192, MAX22088. Those are disallowed for this challenge.To get you started, here's a schematic that would not win any prizes:
Clifford Heath