Varec 4000 - Manual (Page 72)

Optional Interfaces Tank Gauge Transmitter
62 Installation and Operations Manual
10.5 4000WBFMO
This option can co-exist along side Whessoe Bus™ transmitters, the signal format is a current loop style transmission
signal. Transmitter is user selectable between 1 and 127 with basic baud rates stop and parity bits. The protocol is
referred to as Whessmatic 550, which was widely used by the UK for their Intelligent Tang gauging systems. The ATT
meets and exceeds the requirements of the Whessmatic 550 format because of its redundant dual port capabilities,
and the bipolar signal circuitry design. The advanced circuitry allows the ATT to communicate without error at 9600
baud through 2 data ports simultaneously. A typical transmitter using current loop signal format nominally
communicates at 300 to 1200 baud at maximum.
10.6 4000GMFMO
Basically this is identical to the standard release of the 400048FMO, a MODBUS protocol device communicating over
RS-485 data lines. GSI, a tank gauging systems manufacturer has re-mapped level and temperature integer registers
to non-standard MODBUS locations. This version ATT allows it to co-exist along side GSI transmitters and gauging
systems with response data as expected.