Table 1: Logic Level Truth Table

SD

BEEP

DETECT

MUTE

HP

SENSE

MODE

R-

R+

L-

L+

L

L

L

L

BTL SPK

ON

ON

ON

ON

L

L

L

H

HP

ON

ON (buffer)

ON

OFF

L

L

H

L

BTLSPK

ON

ON

ON

ON

*Amps are muted

L

L

H

H

HP

ON

ON (buffer)

ON

OFF

*Amps are muted

*Next four conditions, beep is detected; beep signal added to audio signal and bypasses volume control (unity)

L

H

L

L

BTL SPK

ON

ON

ON

ON

L

H

L

H

HP

ON

ON (buffer)

ON

ON

L

H

H

L

BTL SPK

ON

ON

ON

ON

*Dual Mode

L

H

H

H

HP

ON

ON (buffer)

ON

ON

*Dual Mode

*Next eight conditions turns off all amps

H

L

L

L

BTL SPK

OFF

OFF

OFF

OFF

H

L

L

H

HP

OFF

OFF

OFF

OFF

H

L

H

L

BTL SPK

OFF

OFF

OFF

OFF

H

L

H

H

HP

OFF

OFF

OFF

OFF

H

H

L

L

BTL SPK

OFF

OFF

OFF

OFF

H

H

L

H

HP

OFF

OFF

OFF

OFF

H

H

H

L

BTL SPK

OFF

OFF

OFF

OFF

H

H

H

H

HP

OFF

OFF

OFF

OFF

*Beepdetect signal overrides any mute. For example, if amp is muted and bpdetect is HIGH, then amp is no longer muted.

**Dual mode: When HP jack is inserted, load A (speaker corresponding to outputs A- and A+) is physically disconnected. Load

B remains connected; however, amp B+ is off and differentially there is no voltage across it. If a beep is detected (i.e. beepdetect

= HIGH), then summed signal (audio + beep signals) is heard in the headphones and on speaker B.

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