Lava Computer Serial Port Splitter LAVA POS - Manual (Page 5)

Functional Schematic of Splitter
Data Flow TX/RX
POS expects to see data from some device, at a given time. If the data
is not as expected, then the application program in the POS rejects the
data.
P1 and P2 are "Party-line/multi-dropped" on the RS-232 COM port of
the POS.
POS P1
P2
P3
RS-232
Splitter
Data from P2 or P3
is sent to P1
Data from P1 is
sent to "P2 and P3"
Cheque
reader
Pinpad or
RFID
reader