BECKHOFF KL2521-0000 - Manual (Page 11)

Functional description
KL2521 9
KL2521-0024: Connection to external electronics
For connection to external electronics pay attention that KL2521-0024's
terminal points A- of the first and B- of the second channel are internally
connected to each other.
K
L
2521-
002
4
A B
24V
A+ B+
A- B-
K
L25
21-
002
4
0V
24V
K
L
5151-
000
0
A- B-
A+ B+
A B
K
L25
21-
002
4
0V
24V
K
L
5151-
000
0
A- B-
A+ B+
A B
1 2 3
This allows two channel connections of external electronics, if the
KL2521-0024 switches the grounds of the external device, as shown in
example 1.
i
Note
The Beckhoff incremental encoder interface terminals KL5111, KL5121,
KL5151 and KL5152 require the switching of the positive voltage.
Because the terminal points A- and B- of KL2521-0024 are internally
bridged, the KL2521-0024 is not able to switch the two inputs of the
KL5151-0000, shown in example 2, independently of each other.
So this red crossed application doesn't make sense!
But you can use one channel of the KL2521-0024 to switch one channel of
the KL5151-0000, as shown in example 3.