Control signals

– Alarm Reset (AR): A closed contact between the DSI AR and DSI RET inputs resets (clears) the

MPC4/IOC4T card’s alarm to lockout.

NOTE: The alarm reset input (DSI AR) is edge sensitive and requires a high to low transition to activate the

reset.

– Danger Bypass (DB) : A closed contact between the DSI DB and DSI RET inputs inhibits (bypasses) the

Danger Relay output.

– Trip Multiplier (TM): The closed contact between the DSI TM and DSI RET inputs multiplies

the alarm level by a scaling factor (configurable via software) for adaptive monitoring.

Principle of operation: Detects open or closed circuits on the inputs Alarm outputs

Alarm relays: 4 per IOC4T card.

The MPC4 card can drive the four local relays on the IOC4T card, as well as the relays on 

the RLC16 relay card and/or the IRC4 Smart Relay card via the Raw bus or open collector (OC) bus in the

VM600 chassis.

See Relay Characteristics on page 4 for IOC4T card relay functions.