Why can visitors hear me through the intercom, but I cannot hear them?

If visitors can hear you but you cannot hear them, the intercom’s outgoing audio path is working while the return path is muted, blocked, damaged, miswired, or not being transmitted. Check receive volume and talk mode first, then inspect the entrance microphone, indoor speaker, wiring, app audio routing, network settings, and power under load.

Understand Which Half of the Audio Path Has Failed

Two-way intercom audio uses separate transmit and receive paths. Your microphone, the communication link, and the entrance-station speaker are working well enough for the visitor to hear you. The fault is more likely in the visitor-to-user path: the outdoor microphone, its wiring or network stream, the indoor monitor’s speaker or handset receiver, or the smartphone’s audio output.

This distinction narrows the diagnosis, but it does not prove that every shared component is good. A damaged cable pair, corroded splice, incorrect terminal, weak power supply, or network rule can pass audio in one direction while interrupting the other.

Check Receive Volume, Mute, and Talk Mode First

Increase the communication or receiving volume while a call is active. Ringtone volume and conversation volume are often separate settings. On an indoor monitor, confirm that the handset is seated and operating correctly, the speaker is not muted, and the system is not routing sound to an optional headset or external speaker.

Some intercoms use half-duplex, voice-operated, or press-to-talk communication. If press-to-talk is active, hold the talk control only while speaking and release it to hear the visitor. Holding the control continuously can let the visitor hear you while blocking the return audio. Loud machinery, traffic, wind, televisions, or air-conditioning noise can also cause automatic voice switching to favor the wrong side of the conversation.

Inspect the Outdoor Microphone and Acoustic Openings

The visitor’s voice begins at the entrance-station microphone. Check whether the microphone opening is obstructed by dirt, paint, protective film, insects, spider webs, sealant, water residue, or an incorrectly installed rain hood. Do not insert tools into the microphone opening or use compressed air unless the manufacturer permits it.

Water intrusion, salt-air corrosion, vandalism, and repeated condensation can damage the microphone or its connection while leaving the call button, camera, relay, and speaker operational. If the problem began after heavy rain, pressure washing, cabinet work, or a lightning event, inspect the enclosure, gasket, drainage, cable entries, connectors, and surge protection.

Check the Indoor Monitor Speaker or Telephone Audio Route

If the entrance microphone is working, the receiving device may not be reproducing its audio. Test another indoor monitor, handset, desk station, or registered phone when the system supports multiple answering points. If one station has no incoming sound while another works, the fault is likely local to the first station, its settings, speaker, handset cord, or network connection.

For a telephone or cellular entry call, confirm that the mobile phone is not sending audio to a Bluetooth headset, vehicle system, hearing device, or disconnected speaker. Raise the in-call volume and switch between speakerphone and earpiece. For an app-based intercom, verify the app is current, the call is fully answered, and the phone is not connected to another audio device.

Analog and Two-Wire Systems Need Wiring Verification

Dedicated wired intercoms may use separate microphone, speaker, common, or proprietary bus conductors. A loose microphone-common terminal, reversed pair, high-resistance splice, broken conductor, or incompatible replacement station can create one-way audio. Match every wire to the exact system diagram rather than relying on color.

Disconnect power before moving conductors. Check terminal tightness, cable continuity, shorts between conductors, and resistance through underground splices with both ends isolated. Never use an ohmmeter on an energized circuit. Existing telephone or alarm cable may pass a basic continuity test yet still have corrosion, excess resistance, or electrical characteristics unsuitable for the intercom.

IP, SIP, and App Systems Can Lose One Audio Stream

Network intercoms commonly carry voice as separate real-time audio streams. A call can connect and video can appear even when the incoming audio packets are blocked or routed incorrectly. Check network reachability, audio-device configuration, supported codecs, firmware, firewall rules, NAT handling, RTP port ranges, and SIP settings for the exact system.

One-way audio that occurs only when answering remotely—but not on a local indoor station—strongly points toward the router, firewall, hosted service, cellular connection, or mobile device rather than the outdoor microphone. When available, run the intercom’s built-in microphone and speaker test and save diagnostic logs before changing network settings.

Verify Power While the System Is Communicating

A weak transformer, undersized DC supply, overloaded PoE switch, excessive voltage drop, or corroded power connection can create unstable audio. Measure voltage at the affected station while the camera, display, infrared lighting, modem, and relay are active. A correct no-load reading does not confirm that the supply remains within specification during a call.

Do not increase voltage above the equipment rating. Match AC versus DC, polarity, current or VA capacity, PoE class, wire gauge, and total cable distance. Separate lock power from intercom power when the manufacturer requires it.

Technician’s Corner

Direction Matters When Isolating the Fault

Because the visitor hears you, start with the entrance microphone and your receiving speaker—not the entrance speaker. This prevents replacing the wrong outdoor audio component simply because the problem appears at the gate.

South Florida Moisture Can Create Intermittent One-Way Audio

Humidity and salt residue can raise resistance at microphone terminals and underground splices without causing a complete open circuit. The system may work after drying out and fail again during rain or early-morning condensation.

Do Not Confuse Relay Noise With an Audio Failure

If sound disappears only when the gate-release button is pressed, check power loading, grounding, relay suppression, and shared wiring. The lock or operator command may be injecting noise or pulling the supply voltage down during activation.

Replacement Stations Must Match the System Generation

A visually similar entrance station may ring and release the gate while using incompatible microphone wiring or digital audio signaling. Verify the complete part number, suffix, board revision, firmware, and approved station combinations.

Before You Replace an Intercom Component

• Test receive volume, mute, handset, speakerphone, Bluetooth routing, and press-to-talk operation.
• Inspect the outdoor microphone opening, enclosure, gasket, connectors, drainage, and signs of corrosion.
• Compare performance at every indoor monitor, app, telephone, or guard station.
• Verify wiring terminals, polarity, continuity, splices, cable type, and system-family compatibility.
• For IP or SIP equipment, check audio tests, firmware, codecs, RTP ports, NAT, firewall, and network logs.
• Measure the correct AC, DC, or PoE supply at the station while the system is under load.
• Confirm model number, part number, connector type, voltage, and system generation before replacement.

Related Technical Categories

• Gate and Garage Intercoms
• Intercom Entrance Stations and Microphones
• Indoor Monitors and Handsets
• Intercom Power Supplies and Transformers
• Low-Voltage Cable and Connectors
• IP Intercoms and Network Equipment
• Surge Protection

Before selecting replacement hardware, verify the entrance station, monitor, controller, power supply, and network models; the complete part numbers and revisions; voltage and PoE requirements; wire type and distance; connector pinout; firmware; and communication protocol. Similar-looking microphones, speakers, stations, and boards may not be electrically or digitally interchangeable.