GE 90-30/20/Micro manual Relay Functions, Using Contacts, Types of Contacts

4

Section 1: Relay Functions

This section explains the use of contacts, coils, and links in ladder logic rungs.

Function	Page
Coils and negated coils.	4-3
Normally open and normal closed contacts.	4-2
Retentive and negated retentive coils.	4-4
Positive and negative transition coils.	4-5
SET and RESET coils.	4-6
Retentive SET and RESET coils.	4-7
Horizontal and vertical links.	4-7
Continuation coils and contacts.	4-8

Using Contacts

A contact is used to monitor the state of a reference. Whether the contact passes power flow depends on the state or status of the reference being monitored and on the contact type. A reference is ON if its state is 1; it is OFF if its state is 0.

Table 4-1. Types of Contacts

Type of Contact	Display	Contact Passes Power to Right:
Normally Open	— —	When reference is ON.
Normally Closed	—/—	When reference is OFF.
Continuation Contact	<+>———	If the preceding continuation coil is set ON.

4-2 Series 90-30/20/Micro Programmable Controllers Reference Manual–September 1998 GFK-0467K