Cisco 7000 Series - Null Modem Cable

Cabling Specifications A-13
HSSI Connector Signals
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 HSSI Null Modem Cable Signals
ST - Send Timing 6 <— 31
SG - Signal Ground 7 — 32
TA - DTE Available 8 —> 33
TT - Terminal Timing 9 —> 34
LA - Loopback Circuit A 10 —> 35
SD - Send Data 11 —> 36
LB - Loopback Circuit B 12 —> 37
SG - Signal Ground 13 — 38
5 - Ancillary to DCE 14–18 —> 39–43
SG - Signal Ground 19 — 44
5 - Ancillary from DCE 20–24 <— 45–49
SG - Signal Ground 25 — 50
1. Router is + side (DTE). DSU is – side (DCE).
Signal Name From Pins Direction To Pins Signal Name
Receive Timing 2, 27 —> 9, 34 Terminal Timing
DCE Available 3, 28 —> 8, 33 DTE Available
Received Date 4, 29 —> 11, 36 Send Data
Loopback C 5, 30 —> 10, 35 Loopback A
Send Timing 6, 31 —> 6, 31 Send Timing
DTE Available 8, 33 —> 3, 28 DCE Available
Terminal Timing 9, 34 —> 2, 27 Receive Timing
Loopback A 10, 35 —> 5, 30 Loopback C
Send Data 11, 36 —> 4, 29 Receive Data
Signal Name
Pin No., + Side
(Router End) Direction
1
Pin No., – Side
(DSU End)