V.24: add support for AMBTs/PDUs #68
Description
Regular TSBKs work fine in V.24 mode, but AMBTs are not, as they use V.24 message type 0x87 (PDU). DVMHost supports this in modem mode (DVM/STM32) but not in V.24 mode.
This is to help implement DVRS mode on V.24 repeaters such as Quantars.