APL Ethernet: what type of encoding is used: Manchester?

So the answer to the above question: APL Ethernet does not used Manchester encoding. According to the literature "Ethernet-APL is based on 10BASE-T1L physical layer capability of a full-duplex, dc-balanced, point-to-point communication scheme with PAM 3 modulation at a 7.5 MBd symbol rate, 4B3T coding " https://www.analog.com/en/thought-leadership/ethernet-apl-optimization-of-process-automation.html"

What PAM3 and 4B3T are?

PAM stands for Pulse Amplitude Modulation, it can have three different amplitude levels. So with two consecutive position codes you can have up to 8 different values:

The next figure shows an example of Digital Data conversion to PAM3:

Additional: 4B3T Stands for 4 (four) Binary 3 (three) Ternary. 4B3T represents four binary bits using three pulses. + (positive pulse), 0 (no pulse), and – (negative pulse). When transmitting, the DC bias is tracked and a combination is chosen that has a DC component of the opposite sign to the running total.This mapping from 4 bits to 3 ternary states is given in a table known as Modified Monitoring State 43 (MMS43). Each 4-bit input group is encoded as a 3-symbol group.