Black Box Mixed-Media Fiber Hubs
Installation and User Guide (4/99)
An SPM operating at 100Mbps has a PDV of 50 BT, i.e., the same PDV as a DTE or
NIC card in a Fast Ethernet collision domain.
2.5.4 LH8050A-SRJ
The LH8050A-SRJ is an LH8050A hub with a 10/100 RJ-45 SPM built into the
bonus port. It can connect to devices equipped with an RJ-45 port which supports either
10BASE-T and 100BASE-TX. The 10/100 speed selection is done
with a manual switch on the unit to prevent ambiguity where it may be
used with other devices such as switches that are auto-sensing.
10
0
10
M
b
/s
14
LH8050A-SRJ
The SPM in the LH8050A-SRJ filters and forwards
packets, maintains its address tables, and segments the network when
used as a 10BASE-T or a 100BASE-TX switch port. See Sections 2.5
and 2.5.1 for a general description of an SPM. The SPM in the
LH8050A-SRJ includes an up-link switch to allow for connection to
either user nodes or for cascaded up-link connections to other hubs.
The attached devices may be either 10 Mbps or 100Mbps.
U
P
L
IN
K
R
X
L
IN
K
The SPM in the LH8050A-SRJ has two LED’s - LINK and RX - to allow
monitoring of link and packet reception status of the SPM’s operation.
2.5.5
SPM Specification Summary Table
Connector
Standard
Mb/s
Traffic
Pkt Buffer
Address
LH8050A-SST
Fiber-ST
100BASE-FX
100/200
full-duplex
1MB
8K total
LH8050A-SSC
Fiber-SC
100BASE-FX
100/200
full-duplex
1MB
8K total
LH8050A-SSCSM
Fiber-SC
100BASE-FX
100/200
full-duplex
1MB
8K total
LH8050A-SRJ
RJ-45
10BASE-T & 100 -TX
10 or 100
shared
256KB
1024/port
(See also “Specifications - SPMs,” Section 1.3)
2.6
10 /100 Speed Auto-sensing (LH8050A, front copper ports only)
Twisted pair copper ports (LH8056C, LH8056C-UP only) support auto-sensing for
speed, independent of the other ports. Speed-sensing is performed by the unit’s electronics in
accordance with the specifications of the IEEE 802.3u auto-negotiation standard. If the
connected device or node indicates that it is capable of 100Mbps speed, then operation on that
port will be at 100Mbps. If the connected device does not positively indicate that it is capable
of 100Mbps speed, then the operation on that LH8050A port will be at 10 Mbps. Of course, the
hubs’ auto-negotiation technique is only for 10 / 100 speed, and does not provide for any full-
duplex operation.
