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MA-485 (MA-485) Mircom Intercom Amplifier
Mircom MA-485A is a communications amplifier designed for communication between the IS-489 suite stations and the vestibule (lobby) panel, as well as selective door opening. It incorporates an Automatic Level Control (ALC) circuit that provides clean, clear voice communication in both directions.
Mircom MA-485 amplifier provides AC (buzzing) and DC(silent) door strike action. For multiple vestibule applications, RL-401A relay units are required. One RL-401A relay unit is required for every two-vestibule used.
Amplifiers and relays are normally mounted within the vestibule enclosures. Where such enclosures are located out-doors, the amplifiers and relay unit must be installed in a dry indoor location where the ambient temperature is kept within 32 to 104°F (0 to 40°C). Do not mount transformer closer than 12 inches to the amplifier or vestibule speaker; observe local electrical codes.
Compatible Mircom Suite Stations
IS-401B Standard Suite Station
IS-489 Single Gang Station
IS-489-1 Single Gang Station with Office Call
IS-51-3 Vandal Resistant Dual Gang Station
Compatible Mirtone Suite Stations
IS-401 Standard Suite Station
IS-401-1 Suite Station with Office Call
IS-421 Dual Cone Speaker Station
IS-51-2 Dual Gang Station
IS-485 Single Gang Station
IS-485-1 Single Gang Suite Station with Office Call
Mircom MA-485 amplifier provides AC (buzzing) and DC(silent) door strike action. For multiple vestibule applications, RL-401A relay units are required. One RL-401A relay unit is required for every two-vestibule used.
Amplifiers and relays are normally mounted within the vestibule enclosures. Where such enclosures are located out-doors, the amplifiers and relay unit must be installed in a dry indoor location where the ambient temperature is kept within 32 to 104°F (0 to 40°C). Do not mount transformer closer than 12 inches to the amplifier or vestibule speaker; observe local electrical codes.
Compatible Mircom Suite Stations
Compatible Mirtone Suite Stations
Troubleshooting Mircom Apartment Intercom System
Mircom MA-485 Amplifier
Entire System Dead
Check for 16 VAC at transformer secondary and 120 VAC at transformer primary. Review field wiring and perform direct test using one of the apartment stations to eliminate field wiring.
No Talk
Check wiring to terminals 1 and 3, and check whether wiring to entrance panel speaker is shorted or open. Suite station can be swap tested with another working unit.
No Listen
Check wiring to terminals 1 and 2, or for short between terminals 1 and 2. Check to see if wiring to entrance panel speaker is shorted or open. Suite station can be swap tested with another working unit.
No Door Operation
Check wiring to door release for shorts and opens, or for defective door release. Confirm that shunts are properly set for door release type and that connections to appropriate output have been made. Check wiring to terminals 2 and 3, or 1 and P (depending upon suite station type).
No Call Tone
Check wiring to terminal Z to entrance panel, related entrance panel call buttons, and suite station X terminal. Suite station can be swap tested with another working unit.
Excessive Hum or Distortion Check whether wiring is installed too close to electrical wiring or electrical devices; amplifier installed too close to transformers or other electrical devices; twisted pair wiring not used as required; or amplifier voice volume set too high.
Radio Interference
Connect G terminal from amplifier to electrical ground. Note: This connection is not shown on the wiring diagram, since the situation is not always improved by adding it. If the problem persists, consult the factory or service representative.
Oscillation (feedback or howling)
Reduce the voice volume until oscillation is eliminated. If oscillation stops when the call tone wire is removed from ZW, set entrance tone (SW3) to the OFF (left) position.
Signal Flow and Theory of Operation for MA-485 Amplifier and Apartment Intercom System
The following example describes an apartment intercom system using a MA-485 in conjunction with a 4-wire station.
Call Button
Pressing a suite station call button on the entrance panel routes the call tone from the Z terminal on the MA-485 to the X terminal (tone in) on the associated suite station. This signal then passes through the speaker and returns to the MA-485 via the 1 terminal (audio common).
Talk Button
Pressing the talk button at a suite station connects the suite station’s internal speaker to terminals 1 and 3 of the MA-485, which serves as an audio input to the amplifier. The audio is then amplified and sent to terminals S1 and S2, which are connected to the entrance panel’s speaker (speaker mode).
Listen Button
Pressing the listen button at a suite station connects the suite station’s internal speaker to terminals 1 and 2 of the MA-485, which serves as an audio output from the amplifier. This allows the suite station to receive the amplified audio being received by the amplifier on terminals S1 and S2 from the entrance panel speaker (microphone mode).
Door Button
Pressing the door button at a suite station creates closure between terminals 2 and 3 on the MA-485. This state is sensed by the amplifier and causes the door release to be activated. This state is also triggered by shorting terminals 1 and P as is typically done by a postal lock.
Mircom MA-485 Amplifier
Entire System Dead
Check for 16 VAC at transformer secondary and 120 VAC at transformer primary. Review field wiring and perform direct test using one of the apartment stations to eliminate field wiring.
No Talk
Check wiring to terminals 1 and 3, and check whether wiring to entrance panel speaker is shorted or open. Suite station can be swap tested with another working unit.
No Listen
Check wiring to terminals 1 and 2, or for short between terminals 1 and 2. Check to see if wiring to entrance panel speaker is shorted or open. Suite station can be swap tested with another working unit.
No Door Operation
Check wiring to door release for shorts and opens, or for defective door release. Confirm that shunts are properly set for door release type and that connections to appropriate output have been made. Check wiring to terminals 2 and 3, or 1 and P (depending upon suite station type).
No Call Tone
Check wiring to terminal Z to entrance panel, related entrance panel call buttons, and suite station X terminal. Suite station can be swap tested with another working unit.
Excessive Hum or Distortion Check whether wiring is installed too close to electrical wiring or electrical devices; amplifier installed too close to transformers or other electrical devices; twisted pair wiring not used as required; or amplifier voice volume set too high.
Radio Interference
Connect G terminal from amplifier to electrical ground. Note: This connection is not shown on the wiring diagram, since the situation is not always improved by adding it. If the problem persists, consult the factory or service representative.
Oscillation (feedback or howling)
Reduce the voice volume until oscillation is eliminated. If oscillation stops when the call tone wire is removed from ZW, set entrance tone (SW3) to the OFF (left) position.
Signal Flow and Theory of Operation for MA-485 Amplifier and Apartment Intercom System
The following example describes an apartment intercom system using a MA-485 in conjunction with a 4-wire station.
Call Button
Pressing a suite station call button on the entrance panel routes the call tone from the Z terminal on the MA-485 to the X terminal (tone in) on the associated suite station. This signal then passes through the speaker and returns to the MA-485 via the 1 terminal (audio common).
Talk Button
Pressing the talk button at a suite station connects the suite station’s internal speaker to terminals 1 and 3 of the MA-485, which serves as an audio input to the amplifier. The audio is then amplified and sent to terminals S1 and S2, which are connected to the entrance panel’s speaker (speaker mode).
Listen Button
Pressing the listen button at a suite station connects the suite station’s internal speaker to terminals 1 and 2 of the MA-485, which serves as an audio output from the amplifier. This allows the suite station to receive the amplified audio being received by the amplifier on terminals S1 and S2 from the entrance panel speaker (microphone mode).
Door Button
Pressing the door button at a suite station creates closure between terminals 2 and 3 on the MA-485. This state is sensed by the amplifier and causes the door release to be activated. This state is also triggered by shorting terminals 1 and P as is typically done by a postal lock.
Products Ship From Chicago, IL and Aurora, CO