Mitsubishi Electric MELSEC iQ-F Series Training Manual page 5

Types of relay and timers
As shown below, a PLC incorporates multiple relays, timers and counters with countless N.O. and N.C.
contacts.
A sequential circuit is formed by connecting the contacts and coils.
Also, one advantage of using a PLC is that a lot of storage cases called "data registers" are included.
Auxiliary relay:M
The PLC
incorporates
multiple auxiliary
relays indicated
by the element
symbol M.
Output terminal
Input
Input relay: X
An input relay is an inlet port on the PLC where an external signal provided
from an input switch is received and indicated by the element symbol X.
The PLC incorporates an appropriate number of input relays.
30
20 40
50
10
0
60
SECONDS
STAR DELTA TIMER
Timer:T
The PLC
incorporates
multiple timers
indicated by the
element symbol T.
Data register: D
The data register is used as the storage box for storing the
numerical data and it is indicated by the element symbol D.
Output contact of output relay (single N.O. contact)
The PLC incorporates an appropriate number of
output relays.
Output
TIME
Counter:C
The PLC
incorporates
multiple counters.
They are indicated
by the element
symbol C.
5
Input terminal
Output relay:Y
An output relay is
an outlet port on
the PLC to drive
an external load
and it is indicated
by the element
symbol Y. The
PLC incorporates
multiple output
relays.