https://www.analog.com/en/resources/technical-articles/jj2011compatible-interface-for-the-ds2155-and-ds21455-scts.html
JJ-20.11-Compatible Interface for the DS2155 and DS21455 SCTs | Analog Devices
Supporting the Japanese private branch exchange (PBX) standard JJ-20.11 with the DS2155 or DS21455 Single Chip Transceiver (SCT).