0049-1200-XXX RM16M – USER’S GUIDE 12/29/2010
Rev. C
Page 21
of
27
Pin No. EIA-232C
CCITT
Signal Name
Description
17
DD
115
Receive Clock
A receive data rate clock output for use by
the external data sink. Positive clock
transitions correspond to data transition.
18 141
Local
Loopback
(Loop 3) Control
A positive level will cause the modem to
go into a local analog loop, when strap
enabled.
20 CD 108.2
Data
Terminal
Ready
This circuit is positive when the DTE is
ready to originate or answer a call in dial
up operation. DTR must always be active
(high) in 2-wire private line operation.
Cycling DTR causes retraining.
21 140
Remote
Digital
Loopback
A positive level will cause a digital
loopback at a remote modem, when strap
enabled.
22
CE
125
Ring Indicator
In a direct dial operation, this circuit is
positive in response to an incoming ring
signal.
23
CH
111
Data Rate Select
Supplies a data rate control to select
Primary or Fallback data rate.
24
DA
113
External Transmit
A serial data rate clock input from the data
source. Positive clock transitions
correspond to data transitions.
25
142
Test Mode
Indicates when the modem is in a test
mode.
