6.10.2. CIRCUIT OPERATIONThe TAM INTERFACE circuit consists of an EXT. TAM HOOK detection circuit, CNG signal from the other party’s detection circuit,VOX detection circuit (to judge sound/no-sound) and RL101 (to separate EXT. TAM).1. EXT. TAM HOOK detection circuitA bell is received at EXT. TAM and EXT. TAM is connected to the line, making a DC LOOP. Then, PC101 detects this voltage.During detection, PC101 (4) becomes low.(DC LOOP)Tip → L101 → JJ103 → L105 → Tip1 → (EXT.TAM) → Ring 1 → L104→ RL101(5, 3) → PC101(1, 2) → L102 → POS101 →Ring2. CNG/VOX signal detection circuitThe CNG signal from the other party’s FAX is detected in MODEM IC505 (digital board).(Signal path)Refer to 2.3.7.1. CHECK SHEET(P.74).3. Remote receivingThis is the parallel-connected DTMF signal for the TEL or EXT.TEL mode between T and R. When the other party is a FAX,the unit switches to FAX receiving.(Signal Path)Detects the DTMF signal in the MODEM.168KX-FP81BX / KX-FP81CX / KX-FP82CX
