Introduction to telephone circuitry Flashcards
a direct connection between switching machine and the end users phone or terminating device ____
what are the exceptions?
line
loop terminators, with data terminal or device
going off hook closes ____________ loop to generate a service request and switch returns to dial tone
tip/ring
a touch tone phone dials numbers by generating _________ tones
dual tone multifrequency
when a phone rings what is the ringing voltage?
90vac
a rotary phone generates ______ by making and breaking the loop
dial pulsing
explain the process for outgoing calls from a telephone set.
- the line is idle and the tip is ground from resistance; the ring is -48V. station is on hook
- for outgoing seizure the station set goes off-hook (hookswitch closes the loop)
- seizure recognition
- station set goes on hook and opens the hook
explain the process for incoming calls from a telephone set.
- station on hook the loop is open
- switch applies ringing across tip and ring
- telephone goes off hook and the loop is closed
what was invented by AT&T which allowed major development in telephony technology?
digital trunks
what are the 4 different types of signaling functions
supervisory state
address signaling
information signaling
alerting signals
how is common channel interoffice signaling different from the other signaling protocals
signal info on separate dedicated data channel
list three alerting signals which indicate response requiring conditions to a subscriber, operator or switching system
ringing - notify subscriber of call
flash/hook flash - rapid depression and release of switch hook
receiver off hook - alert subscriber they forgot to hang up
list an advantage of a digital phone compared to an analog phone
less wires needed (multiplexing technique)
the connecting circuit between two switching machines such as two COs a CO and a PBX or two PBXs is called a?
trunk circuit
what are the 4 most common types of trunks
loop start
ground start
direct inward dial
E and M type
trunk circuits operate in the same manner as _______ circuits, but they are shared communication paths between switches, where _________ circuits are individual connections paths from switch to user.
line
what type of trunk circuit improves start signaling between switches and reduces the occurrence of glare?
Ground start
why were the additional wires added to the E and M trunk circuit
provide separate signaling path.
what type of trunk circuit allows an outside caller to directly dial a PBX extension without going through the attendant?
direct inward dial
the on hook and off hook states are represented by the absence or presence of current in the loop. what type of trunk is this?
loop start
a T1 line/carrier has 24 digital channels each channel can transmit at a rate of?
64Kbit per second
a T1 line has a overall transmission rate of
1.54 M bits per second
what is the main difference with a direct inward dial trunk compared to loop and ground start trunks
PBX provides battery towards the Central office
what two types of trunk signaling circuits lack supervision or any kind of reliable disconnect signal?
loop and ground start
define glare
result of simultaneous seizure of a circuit by two parties
what type of signaling function indicates circuit status and call progress to subscribers and operators?
info signaling
what type of signaling function operates between the switch and a subscriber for initiation or termination
supervisory state
