Dascom T2150 RS232C/TTY Interface Module Operators Manual - Manual (Page 6)

Interface Description
Two different serial interfaces are located on this compo-
nent:
– RS232C and
– TTY 20mA.
Different to the standard RS232C interface not all si-
gnals are available.
Whereas the RS232C interface requires one line for the
send and receive line respectively, the TTY interface re-
quires twice as many lines. Here one current loop for
the receive data (Receive Loop (RxLoop)) and one cur-
rent loop for transmission data (Transmit Loop
(TxLoop)) are formed. Data are transmitted when a cur-
rent flow switches or does not switch an optic coupler on
the corresponding current loop. Simultaneously these
optic couplers ohmically isolate the transmission line
from the printer electronics.
It is definitely worth noting that for the TTY interface,
the 20 mA supply can be switched, i.e. either the printer
or the opposite end provide the power. If the printer
provides the necessary power, it is referred to as
the active part. If power comes from the opposite
end it is termed the passive part.
The user/operator must make sure that only one side
function as power supplier. Wrong settings can destroy
components.
STOP
Interface Description
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