Siemens S5-135U/155U - Manual (Page 246)

5-106
System Manual
C79000-G8576-C199-06
5.11.4 TTY Submodule
The TTY submodule is for use with the RK 512 computer link, data
transmission with procedures 3964/3964R, data transmission with the “open
driver.”
The TTY submodule complies with DIN 66 258, Part 1.
The TTY submodule can be inserted in the following CPU:
Interface Submodule ... For Use With ...
TTY submodule CPU 928B
CPU 948
The TTY submodule is equipped with a transmitter and receiver for 20 mA
current loop signals. Shown in the following figure is the typical circuitry for
current loop signals.
Current Direction Arrows
Transmitter
–
Transmitter
–
+
+
–
+
Receiver
–
Receiver
–
–
+
+
+
Figure 5-20 TTY Submodule: Loop Current Direction
The loop current can be fed in both by the TTY submodule and by the
partner station. Only the side supplying the current is non-floating.
!
Caution
With longer line lengths, you should arrange your line so that the transmitter
always supplies the current.
Application
Circuitry
CPUs, Memory Cards, Memory Submodules, Interface Submodules