Ericsson T18s Trouble-Shooting Instruction page 4

1.2 Abbreviations.
A: The power module at some phones.
B: Crystal.
C: Capacitor.
D: Digital circuit.
F: Over voltage protection.
G: VCO.
H: Buzzer, LED, pads for display.
J: Connector.
L: Coil.
N: Analogue circuit, the power module at some phones.
R: Resistor.
S: Keyboard pads.
U: BALUN. A circuit that converts a signal from balanced to unbalanced or the
opposite.
V: Transistor or diode.
X: Contact surface at the circuit board.
Z: Filter.
AGND: Ground for analogue signals.
DCIO: DC voltage used for charging the battery through the system connector.
DCON: Logical signal from the processor that keeps the phone running after
you've released the On/Off key.
EXTAUD: Input signal at the system connector that the processor uses to deter-
mine if there's any external audio equipment attached.
EXTAUDI: The same signal as the EXTAUD signal but at the processor side.
GND: Ground.
LED1G and LED2R:Logical signal used to activate the green or red top indicator.
LED3K: Logical signal used to activate the background illumination.
ONSRQ: Voltage from the On/Off key that starts the phone.
PORTHF: Input signal at the system connector that the processor uses to deter-
mine if there's any handsfree equipment attached.
PHF1: The same signal as PORTHF but at the processor side.
REGON: Logical signal that activates the voltage regulators.
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T18s, T18sc Standard Electrical Repairs
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