Lucent Technologies DDM-2000 OC-3, User & Service Manual

Page: 357 / 2536

363-206-285
Circuit Pack Descriptions
Issue 3 June 2001 7-79
Timing Circuitry 7
The STS1E circuit pack receives timing signals which are traceable to the clocks
generated by the TG circuit packs.
The STS1E circuit pack can select between the supplied timing signals as
requested by the SYSCTL via the intra-shelf control bus. The selected timing
signals are used to time both the receive and transmit directions of the STS1E
circuit pack.
Protection Circuitry 7
Optional 1x1 nonrevertive STS1E circuit pack protection is provided.
In the high-speed mode, the STS1E provides protection switching for the VT-G
side of the low-speed circuit packs. The STS1E can be requested by the SYSCTL
through the intra-shelf control bus to replace any of the seven service VT-G inputs
with the protection VT-G input. The STS1E can be requested by the SYSCTL to
bridge any of the seven VT-G service outputs to the protection output. In the low-
speed mode, the STS1E provides SYSCTL-controlled selectors for the STS-1
side of the main OLIU protection switch.
STS1E circuit pack protection switch points for the STS-1 side are located on the
OLIU circuit packs. Switch points for the EC-1 side are implemented with relays
on the STS1E circuit pack. To ensure that the relays can be operated when the
circuit pack fails, the relay is controlled by the SYSCTL, via the control interface.
Also, if power to the board is lost, the relay switches autonomously to the standby
state. When a new board is inserted, it defaults to the standby state until
provisioned active by the SYSCTL.
On the EC-1 side, a single STS-1 input from an STSX-1 is sent to both the active
and standby STS1E circuit packs. Only the active unit selects the STS-1 input.
The SYSCTL supervises the state of the active and standby units so that the relay
state of each is always the inverse of the other. The hybrid on the active unit splits
the STS-1 input signal and sends it to the standby unit and to its own receiver. To
implement a protection switch on the EC-1 side, the SYSCTL switches the relays
on each unit to their opposite state.
When an STS1E is removed, shorting contacts on the backplane connector
operate so that the STS-1 input signal from its companion unit is returned for
proper termination.