Intercom systems allow instant communications between rooms and buildings. These systems are wired directly between points with no ability to contact locations that are not part of the inter-communication system. Intercoms are reliable, always available and rarely need maintenance. One pesky problem, however, with an intercom system is static on the speaker when listening. Finding and eliminating the static first involves discovering the source.
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An intercom is a microphone for speaking, a speaker for listening, possibly a toggle switch to go back and forth between the two and wires connecting each intercom location. As with any audio equipment, as the intercom ages the speaker can develop wear and eventually no longer produce any sound. Before this happens the wiring connections to the speaker may cause static. The same circumstance can occur with the microphone. Pests, moisture or accident (such as putting a nail in the wall and contacting the wire) can damage wiring in the walls and floors of the intercom location.
Any damage to the intercom equipment can cause static in the system. Static may also be heard on all speakers of the intercom and not just the speaker connected to the particular damaged component.
Although the intercom is a closed system with no broadcasting capability, interference can still cause static. Check all electrical equipment in the same location. Disconnect and reconnect the appliance or electrical component to see if the static stops and starts. If so, check the grounding of the equipment. Poor grounding can cause audible static throughout the location connected to the same electrical source.
Check for any radio broadcast source near the intercom location. A utility worker operating near the building may be using a two-way radio. The radio broadcast frequency may interfere with the intercom's system. If this is the case, the static may dissipate when the radio moves on to another location.
Intercoms are powered by the location's electrical source. Problems with the power connection may manifest as audible static. If so the static may be a red flag indicating larger problems that can be prevented. Power overloads or shorting could severely damage the intercom. Repairing the power circuit (such as replacing wiring or the circuit breaker) may result in a clear intercom signal.