Tall communications antennas act as lightning rods, sometimes attracting electrical discharges from static build-up in low-hanging clouds. This can damage the input circuitry in communications equipment. The Model 1047 employs a spark gap which shunts currents harmlessly to ground.
In the event of a direct hit by lightning, the Model 1047 can shunt electrical energy to ground, lessening or possibly eliminating damage to communications equipment.