Cabling and Interface Pinouts B-3
Interface
Pinouts
12 CI 112 Data Signal Rate
Indicator
CI (112) is passed from modem to terminal, indicating signaling rate.
When signal is on, modem operates at 2400 bps or greater. When
signal is off, modem operates below 2400 bps.
13 —110 Signal Quality Signal p asses from modem to terminal indicating signal quality of
telephone line. When signal is on, signal quality is acceptable. When
signal is off, signal quality is poor.
14 —— Ext Select (All models.) Signal passed from terminal to modem to select between
two option sets. Works in conjunction with Ext Select option.
(Models 3261/3263/3266/3268 only.) Signal passed from terminal to
modem indicating whether to use a dial line or a leased line. When
signal is on, modem uses a dial line. When signal is off, modem uses a
leased line. This signal is used in Restoral mode only.
15 DB 114 Transmitter
Signal Element
Timing
Local modem sends an internally generated transmit timing signal to
local terminal to synchronize transmitted data (TXD). See
Clock=Internal.
16 —117 Standby Indicator (Models 3261/3263/3266/3268 only.) Signal passed from modem to
terminal indicating type of l ine in use. When signal is o n, modem is on
a dial line. When signal is off, modem is on a leased line. This signal is
used in Restoral mode only.
17 DD 115 Receive Signal
Element Timing
Timing signal extracted from the received carrier. Local modem
transmits this signal to the DTE to synchronize received data (RXD).
18 —141 Local Analog
Loopback Test
Initiated at local terminal and passed to local modem, causing it to
initiate local analog loopback test.
19 —— — Not used.
20 CD 108.1/
108.2
Data Terminal
Ready (DTR)
108.1—Sent by DTE; causes the modem to connect to the phone line.
108.2—Sent by DTE; allows the modem to connect to the phone line.
21 —140 Remote Digital
Loopback Test
Signal initiated at local terminal and passed to local modem, causing it
to initiate remote digital loopback test (V.54 Loop 2).
22 CE 125 Ring Indicator
(RI)
Passed from local modem to local terminal. On during ringing, off
between rings and when no ring received.
23 CH/CI 111/112 Data Signal Rate
Select/Indicator
CI passed from modem to terminal indicating signaling rate. CI is set
high for data rates greater than 2400 bps; otherwise, it is set low. CI is
also set low while the modem is disconnected. The function of this pin
is determined by the setting of rear panel Switch 1. CH (input) signal
has no effect on modem operation.
24 DA 113 External Signal
Element Timing
Transmit timing signal generated by some synchronous DTEs,
providing clock to the local modem. See Clock=External setting.
25 —142 Test Indicate (TI) Local modem signals to local terminal when local modem is in test.
The terminal can initiate a Busy Out condition on this circuit. The
status of this signal is determined by the status of rear panel Switch 2
and front panel option DTE Pin 25 configured for Test or Busy.
Table B-1. Modem/Computer Interface Connections (Continued)

Pin

EIA/TIA

232-D ITU V.24 Signal Definition