(a)  The dot-bar matrix annunciator in the HDG HOLD switch/light lights when the MCP receives HDG HOLD OPER from the FCCs. HDG HOLD OPER is also sent to the EIUs to display HDG HOLD on the PFDs.

 (7)  
Pressing the ALT HOLD mode select switch/light initiates an altitude hold mode request discrete. This discrete generates a manual ON signal which arms the altitude hold mode if the FCC is engaged in CMD or the F/D is on and the airplane is airborne.

 (a)  The dot-bar matrix in the ALT HOLD switch/light lights when the MCP receives ALTITUDE MODE OPER from the FCC(s). ALT HLD OPER is also sent to the EIUs to display ALT on the PFDs.

 (8)  
Pressing the THR mode select switch/light initiates a thrust mode request discrete. This discrete results in a thrust mode select signal if the autothrottle (A/T) is armed and operating with no faults while the airplane is either on the ground, in the air, or in the takeoff mode.

 (a)  The dot-bar matrix in the thrust mode select switch/light lights when the MCP receives THRUST MODE OPER from the FMC.

 (9)  
Pressing SPD switch/light initiates a speed mode request discrete. This discrete generates a speed mode select signal if the A/T is enabled and the airplane is airborne. The speed mode can also be generated by FL CH mode or VNAV mode disengagement.

 (a)  The dot-bar matrix in the SPD switch/light lights when the MCP receives SPEED MODE OPER from the FMC.

 (10)
 Pressing the Flight Level Change (FL CH) mode switch/light, with the autothrottle ARMED, initiates a flight level change discrete. This discrete generates a flight level change select signal if the FCC is engaged in CMD or the F/D is on.

 (a)  The dot-bar matrix in the FL CH switch/light lights when the MCP receives FLIGHT LEVEL CHANGE OPER from the FCCs. FLIGHT LEVEL CHANGE OPER is also sent to the EIUs to display FLCH SPD the PFDs.

 (11)
 Pressing the Lateral Navigation (LNAV) mode select switch/light initiates an LNAV mode request discrete. This discrete generates an LNAV SELECT signal if the FCC is engaged in CMD or the F/D is on. The LNAV SELECT signal arms the LNAV mode. The LNAV mode can be manually disabled by pressing the LNAV switch/light a second time.

 (a)  The dot-bar matrix in the LNAV switch/light lights when the MCP receives LNAV OPER from the FCCs. The LNAV OPER signal is also sent to the EIUs to display on the PFDs.
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 (b)  The same signal that lights the LNAV switch/light is provided, by the MCP, to the Flight Management Computer System (FMCS) to enable LNAV steering commands from the FMC (Ref 34-61-00/001).
 (12)
 Pressing the Vertical Navigation (VNAV) mode select switch/light initiates a VNAV mode request discrete. This discrete generates a VNAV SELECT signal if the FCC is engaged in CMD or the F/D is on. The VNAV SELECT signal arms the vertical navigation mode and VNAV is displayed white on the PFDs. The VNAV ARM mode can be manually disabled by pressing the VNAV switch/light a second time.

 (a)  
The dot-bar matrix in the VNAV switch/light lights when the MCP receives VNAV OPER from the FCCs. The VNAV OPER signal is also sent to the EIUs to display the appropriate VNAV mode (VNAV PTH, VNAV SPD or VNAV ALT) on the PFDs.

 (b)  
The same signal that lights the VNAV switch/light is provided, by the MCP, to the FMCS to enable VNAV steering commands from the FMC (Ref 34-61-00/001).

 (13)
 Pressing the localizer (LOC) mode select switch/light initiates a localizer mode request discrete. This discrete generates a LOC MODE request signal if the FCC is engaged in CMD or the F/D is on. The LOC MODE signal arms the localizer mode and LOC is displayed white on the PFDs . The LOC ARM signal can be manually disabled by pressing the LOC mode switch/light a second time.

 (a)  The dot-bar matrix in the LOC switch/light lights when the MCP receives LOC MODE ARM/OPER. LOC MODE OPER is also sent to the EIUs to display LOC on the PFDs once the LOC engage logic is satisfied.

 (14)
 Pressing the Approach (APP) mode select switch/light initiates an approach mode request discrete. This discrete generates an APP MODE request signal if the FCC is engaged in CMD or the F/D is on. The APPROACH MODE request signal arms the approach mode. If glideslope and localizer are armed, the APP mode may be disabled by pressing the APP switch/light a second time.
　
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