Null Modem Cable - Cisco 7000 Series Hardware Installation And Maintenance Manual

Signal Name
ST - Send Timing
SG - Signal Ground
TA - DTE Available
TT - Terminal Timing
LA - Loopback Circuit A 10
SD - Send Data
LB - Loopback Circuit B
SG - Signal Ground
5 - Ancillary to DCE
SG - Signal Ground
5 - Ancillary from DCE
SG - Signal Ground
1. Router is + side (DTE). DSU is – side (DCE).

Null Modem Cable

The null modem cable (CAB-HNUL) can connect two routers directly back to back. The two routers
must be in the same location and can be two Cisco 7000 series, two AGS+ routers, or one of each.
A null modem connection allows you to verify the operation of the HSSI or to link the routers
directly in order to build a larger node.
The null modem cable uses the same 50-pin connectors as the HSSI interface cable, but uses the
pinouts listed in Table A-15. For null modem cable connection and configuration instructions, refer
to the section "HSSI Connection Equipment" in the chapter "Preparing for Installation."
Table A-15
Signal Name
Receive Timing
DCE Available
Received Date
Loopback C
Send Timing
DTE Available
Terminal Timing
Loopback A
Send Data
Pin No., + Side
(Router End)
6
7
8
9
11
12
13
14–18
19
20–24
25
HSSI Null Modem Cable Signals
From Pins
2, 27
3, 28
4, 29
5, 30
6, 31
8, 33
9, 34
10, 35
11, 36
Pin No., – Side
1
Direction (DSU End)
<— 31
— 32
—> 33
—> 34
—> 35
—> 36
—> 37
— 38
—> 39–43
— 44
<— 45–49
— 50
Direction To Pins
—> 9, 34
—> 8, 33
—> 11, 36
—> 10, 35
—> 6, 31
—> 3, 28
—> 2, 27
—> 5, 30
—> 4, 29
HSSI Connector Signals
Signal Name
Terminal Timing
DTE Available
Send Data
Loopback A
Send Timing
DCE Available
Receive Timing
Loopback C
Receive Data
Cabling Specifications A-13