Elster V100 T110 Reed Switch

The T110 Pulse probe is fitted with a 100Ω series resistor to protect the reed switch
from power surges and is usually provided with a 5 metre length of
cable, terminating in a sealed flying lead.

For ‘TL2’ variant, the RED and BLUE cores are the volt free pair. The
loop-back is across the BLACK and YELLOW cores. These connections
are not otherwise polarity sensitive.

Note: The reed switch assembly is rated at 50 Vdc maximum working.
The duty cycle of the switch closure is typically 70% on, 30% off.