I have a very strange problem with One of the KTEK Level Transmitter (HART). This device is connected to Honeywell Safety Manager FTA and this FTA is connected to MTL 4840 series HART interface module BPHM64. This KTEK Tx communicates right at the FTA terminals with 375 but do not communicate with Multiplexer. There are other devices in the FTA which communicates to the multiplexer. We have tried changing FTA and multiplexer as well but no help. Any idea ? thoughts what could be the probable reason.