Panasonic KX-TG2226B Service Manual page 57

17.5. Locator/Intercom Mode
1. When the base unit LOCATOR/INTERCOM button is pressed, a call
monitor signal (intercom sound) is output from DSP (SPP, SPN).
Thus a monitor tone is heard from the speaker.
2. At the same time, flashing of the IN USE/CHARGE (LED900) is
obtained from DSP (INUSE-LED). This status is called "Intercom
stand-by".
3. The receiving signal flows:
RF DSP (SPP, SPN)
4. The transmission signal flows:
MIC C235, C236
SP
R213, R214
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DSP (MIN, MIP) RF