CANOGA PERKINS 2240 Fiber Optic Modem - Manual (Page 53)

Chapter 4 Data Interfaces
CCITT V.35 (ISO 2593-1993) Model 436
53
None of the control leads interact with the data transmission. They are provided in order to
comply with a variety of DTE interface requirements. Most of the control leads are actually end-
to-end signal channels which can be used for any purpose as long as it conforms to the V.35
interface standards.
The RTS, CTS and DCD pins function together to provide the most common handshake
functions. An input to RTS (see description of RTS-Bias jumper) is transmitted to the DCD output
at the other end of the link (see description of DCD jumper). CTS follows RTS locally but it is
delayed by approximately 1 msec when RTS turns on (see description of CTS-Gate jumper).
There are two other end-to-end control lead pairs. They are listed below with the input signal
listed first:
• DTR to RI
• STD to SRD
Data Set Ready (DSR) typically indicates that the modem is ready to handle transmit data.
During loopbacks, the behavior of this signal is dependent on the position of the DSR jumper
(see description of DSR jumper). Test Mode (TM) is turned ON (asserted) ONLY when a
loopback is active on either one or both modems.
Local Loopback (LL) and Remote Loopback (RL) are loopback control leads and perform the
same functions as the 2240 front panel LOOP switch, LOC and REM positions. LL and RL are
interface signal inputs which can be used to activate the LOC or REM loop functions. These
signals can control the loopback functions only if the front panel switch is in the center or OFF
position.
4.5.1 RTS_BIAS Jumper
The RTS_BIAS jumper controls the state that RTS floats to when there is no signal driving the
RTS pin. The OFF position forces this signal to the OFF (negated) state when the interface cable
is disconnected. The ON position forces it to ON (asserted).
Factory Setting= OFF
4.5.2 DCD Jumper
The DCD jumper determines the source of the DCD output. In the CTRL position, the DCD
output functions as the output for the RTS input at the far end. In the CD jumper position and with
local RTS ON, CTS will turn ON either when the modem’s fiber optic receiver is in sync (main
PCBA internal switch S1 CD/DCD = OFF and CD/SYNC = ON) or the state of the RTS signal at
the far end (main PCBA internal switch S1 CD/DCD = ON and CD/SYNC = OFF). Refer to
section 2.1.3.1 for more information on the internal switch S1 CD/DCD and CD/SYNC positions.
Factory setting: CTRL
Remote Loopback D D 140 to modem
Table 4-7. Pinout Differences (-435 vs. -436)
Function Pin (A/B)
CCITT Circuit
Number
Direction