Note: The selective calling (SELCAL) system installation is available via optional SB 350-23-002.

The selective calling (SELCAL) system (option) helps the flight crew to monitor the radio frequencies.

The SELCAL system tells the flight crew that the aircraft received a SELCAL signal from a ground high frequency (HF), very high frequency (VHF) transceiver, or satellite communications (SATCOM) satellite data unit (SDU).

The flight crew manually tunes the airborne transceiver, which received the SELCAL signal, to the correct frequency. The flight crew transmits to the ground transceiver through voice.

Note: For the HF SELCAL option, it is necessary to install two HF transceivers.

The SELCAL function is done through the two radio interface units (RIUs) that are installed in the LH and RH equipment racks.

A SELCAL code is given to each aircraft by the aeronautical radio incorporated (ARINC). The code is composed of four audio tones designated by letters, transmitted in two individual pulses.

Ground personnel sends a SELCAL code pulse to an aircraft and starts the SELCAL function. The aircraft receiver decoder automatically monitors for the unique code.

When the aircraft SELCAL code is received, the RIU sends the signal to the data concentrator unit (DCU). The DCU causes the display of the applicable visual indication and sets the aural indication sequence. The DCU gives the aural indication sequence to the RIU. The RIU will then give the aural indication to the flight crew.

The receiver can be an HF radio or VHF radio or the SATCOM SDU and must be manually tuned. When the crew tunes the radio that received the SELCAL code, the CAS message for that radio is removed.

SELCAL System Interfaces

The VHF radio receives the SELCAL code in the VHF band, and the HF radio receives the SELCAL code in the HF band. The satellite communication (SATCOM) satellite data unit (optional) receives the SELCAL code in the L band from the INMARSAT satellite constellation.

The RIU No. 1 controls the SELCAL code detection of the HF transceiver No. 1. The RIU No. 1 supplies the SELCAL code to the VHF transceivers No. 1 and No. 3 (Option). The VHF transceivers do a SELCAL code search.

The RIU No. 1 tells the DCU when a SELCAL coded pulse pair is received from a ground transceiver. Also, the RIU No. 1 sends related digital data to CDU No. 1 and CDU No. 2.

The RIU No. 2 controls the SELCAL code detection of the HF transceiver No. 2. The RIU No. 2 supplies the SELCAL code to the VHF transceiver No. 2. The VHF transceivers do a SELCAL code search.

The RIU No. 2 tells the DCU when a SELCAL coded pulse pair is received from a ground transceiver. Also, the RIU No. 2 sends related digital data to CDU No. 1 and CDU No. 2.

The RIU No. 1 controls the SELCAL code detection of the SATCOM SDU. The RIU No. 1 supplies the SELCAL code to the SATCOM SDU. The SATCOM SDU does a SELCAL code search.

The RIU No. 1 tells the DCU when a SELCAL coded pulse pair is received from a ground transceiver. Also, the RIU No. 1 sends related digital data to CDU No. 1 and CDU No. 2.

SELCAL Datalink

On A/C Post SB 350-23-004

The RIU No. 1 controls the SELCAL code detection of the SATCOM satellite data unit (SDU) or the VHF communication No. 3 (Option). The RIU No. 1 supplies the SELCAL code to the SDU.

The RIU No. 1 tells the data concentrator unit (DCU) when a SELCAL coded pulse pair is received from a ground transceiver. Also, the RIU No. 1 sends related digital data to CDU No. 1 and CDU No. 2.

When the SELCAL code is received, the DCU causes a SELCAL message to show on the control display unit (CDU). The DCU also causes the RIU to give a SELCAL chime.

The messages that can show on the CDU are as follows:

• SELCAL HF1
• SELCAL HF2
• SELCAL VHF1
• SELCAL VHF2
• SELCAL VHF3 (Optional)
• SELCAL DATALINK (On A/C Post SB 350-23-004)

Note:
Also, when the SELCAL code is received, the applicable SELCAL message shows on the EICAS, and a SELCAL aural voice is heard in the flight compartment.

The RIU removes the message of SELCAL, when the push-to-talk (PTT) switch for the radio that received the SELCAL code is pushed.

Selection of the SELCAL code and the related SELCAL displays show on the two CDU pages that follow: 

TUNE 2/2 Page

The TUN pushbutton, on the CDU, when pushed, shows the TUNE page 1/1. Then, when the NEXT pushbutton on the CDU, is pushed, the TUNE page 2/2 shows. The TUNE page 2/2 shows a SELCAL display.

Also, when applicable, the TUNE page 2/2 shows a cyan OFF annunciation to the left of the SELCAL display, to tell the flight crew that the SELCAL detection function is off.

The SELCAL line-select key on the TUNE page 2/2, when pushed, gives access to the SELECTIVE CALLING page.

SELECTIVE CALLING Page

On the SELECTIVE CALLING page, the four letter SELCAL code is entered in the scratch-pad. The CODE line-select key, when pushed, moves the SELCAL code from the scratch-pad to the CODE data field. To disarm SELCAL, the code AAAA must be entered in the scratch-pad. The AAAA code automatically sets DETECTION to OFF.

The DETECTION line-select key on the SELECTIVE CALLING page, when pushed, makes the selection ON or OFF for the SELCAL detection function. If the SELCAL code AAAA is entered, the ON function cannot be made. A white INVALID CODE message shows on the CDU for one second.

The four letter SELCAL code shows on the CDU as follows:

• In green, for three seconds after entry by pilot
• In yellow, if the RIU does not accept the SELCAL code
• In white, while the DETECTION is OFF.

The DETECTION ON/OFF shows on the CDU as follows:

• A cyan OFF shows on the TUNE page to the left of SELCAL
• A cyan ON (for detection on) shows on the SELECTIVE CALLING page
• A cyan OFF (for detection off) shows on the SELECTIVE CALLING page.

The SELCAL system is not in the correct configuration if:

• The local SELCAL code is a valid four letter code other than AAAA, and the RIU reports that it is not in the correct configuration
• The RIU finds a difference between the internal SELCAL code and the SELCAL code from the same-side CDU (between L-CDU and L-RADIO or between R-CDU and R-RADIO)
  
  
• The CDU finds a difference between the SELCAL code from the left and right RIU or the second CDU.

A SELCAL configuration error occurs when the detection function is ON and the SELCAL system is not in the correct configuration. In this condition the messages that follow will show:

• A yellow CNFG ERR message shows on the TUNE 2/2 page above the SELCAL legend
• A yellow SELCAL CONFIG ERROR shows on the CDU SELECTIVE CALLING page

When a SELCAL configuration error occurs, the SELCAL code from the two CDUs and the two RIUs can show on the SELECTIVE CALLING page (in the L-CDU, L-RADIO, R-CDU, and R-RADIO data fields).

When the SELCAL code, from one of the four sources, is the same as the CDU code (shown in the CODE data field), the SELCAL code shows in white. The SELCAL code shows in yellow when it is not the same as the CDU code. The SELCAL code is replaced by four white dashes when it is not received from one of the four sources.

When the DETECTION function is OFF and SELCAL is not in the correct configuration, the SELCAL code, from up to four sources, can show on the SELECTIVE CALLING page. The SELCAL CONFIG ERROR does not show. When the DETECTION function is ON, the SELCAL codes show the same as when the DETECTION function is OFF.

When the aircraft SELCAL code is received, the DCU causes one of the messages that follow to show on the EICAS:

• The SELCAL HF1 (2) advisory message, which shows when a SELCAL code is received by one of the HF receivers
• The SELCAL VHF1 (2) (3) advisory message, which shows when a SELCAL code is received by one of the VHF receivers
• The SELCAL DATALINK advisory message, which show when a SELCAL code is received by the SATCOM SDU or the VHF communication unit No. 3 (On A/C Post SB 350-23-004)

The EICAS messages that follow are related to the SELCAL system: 

EICAS MESSAGES	LEVEL (COLOR)
SELCAL HF1	ADVISORY (cyan)
SELCAL HF2	ADVISORY (cyan)
SELCALVHF1	ADVISORY (cyan)
SELCAL VHF2	ADVISORY (cyan)
SELCAL VHF3	ADVISORY (cyan)
SELCAL DATALINK	ADVISORY (cyan)

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