Tally T2265 SprintPro, Maintenance Manual

Page: 45 / 178

3.3.3.3
TTY Interface 20 mA
The interface signals generated in the microprocessor and in the application’s
specified IC are connected to the interface optocoupler IC1 (Type SFH 618).
This IC switch the TTL-signals on the microprocessor side to the level of the current
loop without any galvanical contact.
Received signals on the Rx loop should be changed by the optocoupler IC2 from
current loop level down to TTL-level (Type HCPL 4200).
DIP switches (S1, S2) are provided to select Active, Passive, (TX, RX).
+TXLOOP
-TXLOOP
-RXLOOP
GND*
25
24
23
22
21
20
19
17
18
16
X2
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
CHASSIS
+RXLOOP
B5
27
C6 33N
63V M
62130
L4 BLM31
CHASSIS
26
Functional Description Electronic Functions
3-27