IDEC SmartRelay functions
195
IDEC SmartRelay Manual 
4.4.21 Latching relay
Short description
Input S sets output Q, input R resets output Q again. 
Timing diagram
Switching response
A latching relay represents a simple binary element. The out-
put value depends on the status at the inputs and on the pre-
vious output status. The following table shows the logic once 
again:
When retentivity is enabled, the current status of the output 
signal is retained after a power failure.
Symbol in
IDEC 
SmartRelay
Wiring Description
Input S You set output Q with a sig-
nal at input S.
Input R You reset output Q with a 
signal at input R. If S and  R 
= 1, the output is reset.
Parameter Retentivity:  
/ = No retentivity 
R = The status is retentive.
Output Q Q is set with a signal at input 
S, and reset with a signal at 
input R.
SR QComment
0 0 x The status is retentive
0 1 0 Reset
10 1Set
1 1 0 Reset (takes priority over Set)
S
R
Q
Courtesy of Steven Engineering, Inc. ● 230 Ryan Way, South San Francisco, CA 94080-6370 ● General Inquiries: (800) 670-4183 ● www.stevenengineering.com