Smart Combination Relays The TF1170 series self-switching combination relay are designed to switch two relays when the vehicle alternator is charging the battery.

The normal operating environment is a 12-volt DC circuit within a motor vehicle. Application. Typically these relays are used in an towbar auxiliary electrical circuit to switch the split-charging and fridge circuits on and off.

They do not need any dedicated signal feed to the coils of the relays.

When the voltage in the line from the battery reaches the appropriate level as the alternator begins to charge the battery, the trigger unit switches the relays on.

When the alternator ceases to charge and the voltage drops, it switches the relays off.