In case anyone ends up here looking for an answer, the relevant chips are the SN75121 and SN75122 for transmission lines and the SN75123 and SN75124 for IBM 360

In case anyone ends up here looking for an answer, the relevant chips are the SN75121 and SN75122 for transmission lines and the SN75123 and SN75124 for IBM 360 bus-and-tag I/O (Signetics N8T13, N8T14, N8T24). The relevant IBM spec is: https://bitsavers.org/pdf/ibm/370/channel/GA22-6974-4_360_370_IO_Interface_Channel_to_Control_Unit_OEM_Information_Jan78.pdf https://bitsavers.org/pdf/ibm/370/channel/GA22-6974-4_360_37...