Alcatel-Lucent 7750 SR-a4, Installation Manual, Page: 219 / 232

Appendix D: CPM-a Pinout Assignments
7750 SR-a4 and SR-a8 Installation Guide 219
RTN refers to the negative side of the Alarm-In connections when a floating power supply is
used. If an external power supply is used as the voltage source for Alarm-In 1-4, its negative
rail must not be connected to chassis ground and it should be 18 to 50 VDC at 100 mA.
When using the internal isolated 24 VDC power supply on pin 4 of the DB15 connector, the
Alarm RTN pins must be connected to chassis ground. The metal shell of the alarm plug may
be used as a chassis ground connection for the in24 VDC supply providing that the
plug mounting (hold down) screws are firmly attached to the alarm connector.
Major and Critical alarm dry relay contact outputs are provided on pins 3, 10, 11, and 1, 2, 9.
These reflect the Major and Critical alarms output by the chassis and can be manually cleared
by pressing the ACO button.
The four alarm inputs are customer configurable to monitor alarms provided by additional
equipment. See
Figure 82 . These inputs must use one of the following:
• the voltage source provided on pin 4 of the DB15 connector
• a separate isolated DC power supply, rated between 18 to 50 VDC at 100 mA
If an external power source is used, its outputs must be isolated from chassis ground, as
shown in
Figure 83 . Do not connect the alarm power supply return to the chassis or rack
ground in this scenario.
Figure 82: Alarm Inputs using DB 15 Alarm Connector
off a ctive
Al a rm 1
+24VDC
7750 SR- a
Extern a l Al a rm Rel a y s
On Other Eq u ipment
- Ch ass i s Gro u nd
Pin 4+
off a ctive
Al a rm 2
off a ctive
Al a rm 3
off a ctive
Al a rm 4
Al a rm DB15
Pin 15-
Pin 8+
Pin 14-
Pin 1 3 -
Pin 12-
Pin 7+
Pin 6+
Pin 5+
Al a rm in 2
Al a rm in 1
Al a rm in 3
Al a rm in 4
24598