Section 3: Series 3700A cards power usage
Series 3700A Switch and Control Cards Reference Manual
3-8
3700AS-909-01 Rev. B / December 2011
Figure 2: Simplified interlock circuit
Engaging hardware interlocks
To engage the hardware interlocks, you must provide a low-resistance path between the two
applicable interlock pins as shown in the diagram. This path routes a 5 V power source to an onboard
interlock relay which in turn enables power to the backplane relays. If a 37xxA-ST accessory terminal
board is used, this low resistance path is provided to automatically engage the interlock circuit.
NOTE
Do not use the supplied 5 V power source for anything other than energizing the interlock relay. It is
not designed for external circuit use.
Be sure to provide a low resistance path between the interlock pins for reliable operation. Significant
resistance if present can cause the interlock circuit to fail to engage.
Interlock status
Some switching cards have more than one interlock. At any time, the current status of each interlock
can be determined by using the appropriate
slot[X].interlock.state remote
ICL command.
When the interlock status reports engaged, associated backplane relays are allowed to be energized.
When the interlock status reports disengaged, associated backplane relays are prevented from being
energized.
Refer to the Series 3700A Reference manual (part number: 3700AS-901-01) for more information on
interlock related commands and details.