Panasonic UF-E1 Service Manual page 139

6.2.4. NCU/TEL Circuit
• The NCU circuit consists of the network control section, which connects the circuit and detects circuit
conditions, and connection switching control section for the extension telephone.
• The telephone circuit section is composed of circuits extending from the NCU circuit via T1 transformer to
the analog circuits in the SC circuit.
Circuit Diagram
L1 Loop Detection
Circuit
L2
RL1
CML
a
T1
b
Extension Phone
Terminal
a
T2
b
Operational Description
Calling Operation
• When Power is OFF
As is shown in the above diagram, when the power supply is OFF, the circuit is connected to the exten-
sion telephone. It is possible to transmit calls from the extension telephone, only when the extension tele-
phone is connected.
Caution
The telephone handset cannot be used when the power is off (i.e. at the time of black out or when the
power cord is pulled off from the outlet.) Also, if the power is cut while making a call, the call is also cut.
• When power is ON
It is possible to make a call by operating from the handset. It is possible to transmit calls from the exten-
sion telephone, when it is connected. (The CML relay is normally connected on the circuit side (a-side)
and the off-hook of the extension phone is detected by the loop detector.)
1. Operation when calling from the handset
• When the handset goes off-hook (hook switch signal) or when the monitor button is pushed (key sig-
nal), this is detected by the CPU (IC15). The CPU (IC15) closes RL1 and the circuit is connected.
• In response to numbers input from the ten-key, DP or PB signal is transmitted to the circuit. Then, the
dialing information is transmitted from the panel (IC1) to the CPU. In recognition of this, the CPU dis-
plays the dialed number on the LCD in the panel section.
NCU Section
T1
PDL
T2
FAXGND
PC3
GND
Speaker on the unit
Handset
Hook Switch
GND
Key Matrix
HYB
IC11
HSIG
(Cross-Point IC)
LA8522M
RING
IC1 (ASIC)
DZAC000218
PNL Section
135
UF-E1
SC Section
IC2
(Modem AFE)
STLC7550TQF7
Transmission
Reception
IC14 Voice AFE
VOICE_TX
STLC7550TQF7
VOICE_RX
IC15 (CPU)
MN195005