SYSTEM TECHNICAL MANUAL
HARDWARE DESCRIPTION
TR A N S M IT D AT A
(TD)
Serial (5-8 B it) data transm itted by the com
puter. Logic ‘ 1’ is low, logic '0 ' is high. Between
character transmissions this signal w ill be low.
RECEIVE DATA
(RD)
Serial (5-8 Bit) data received by the term inal.
Logic '1 ' is low, logic '0 ' is high. Between
characters this signal must be low.
CLEAR TO SEND
(CTS)
Inp ut to the computer, must be high fo r data
transmission.
REQUEST TO SEND
(RTS)
This o utpu t indicates tha t the term inal wishes
to transm it. In the no modem mode this signal
is always high. In the modem and half duplex
modes, this signal is low, when there is no
data fo r the term inal to transm it, and high
when the term inal wishes to transm it.
D A T A S E T READY
(DSR)
Input to the computer, must be high fo r
data transmission in the modem mode. This
signal is ignored in the no modem mode.
D A TA TE R M IN AL
REA DY (DTR )
O utput indicating tha t the com puter is ready
to receive data.
D A T A SIG NA L
RATE SELECT
(DSRS)
Controls a feature of some modems which
allows them to transm it at tw o d ifferent
signalling rates. On = high signal rate. This
signal (ON state = 12V) can also be used fo r
jumpers in modemless operations.
TR ANS M ITTER
S IG N A L ELEM EN T
TIM IN G (TSET)
External clock fo r transm itter
RECEIVER SIG NA L
ELE M ENT TIM IN G
(RSET)
External clock fo r receiver
CARR IER DETECT
(CD)
Input from the modem. This signal indicates
that the (CD) modem is correctly receiving
the data carrier signal from the remote modem.
This line must be high fo r receiving data.
Figure 2.41 RS-232-C signals
2-61
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