CCNA Voice Study

So these are more or less notes for myself, I am starting study for the CCNA Voice exam and will be posting notes here as typing and reading are just two ways to reinforce the knowledge.

Loop start signaling – Is a process in which the end point connects the tip / ring connections together to complete the circuit.

Ground start signaling – A process in which a ground signal is sent to the CO to signal that an outgoing call is going to proceed. Typically used in a PBX.

Glare – When an end user picks up the phone at the same time as an incoming call, occurs with the use of loop start signaling.

Dual-tone multifrequency (DTMF) – The keys on the phone generates two tones a high and a low frequency. AKA tone dialing verses pulse.

Pulse dialing – a process in which the phone quickly connects and disconnects the local loop circuit wires, sending a series of “pulses” to the CO to designate what number is being pressed.

Pulse-amplitude modulation (PAM) – The process of sampling an analog waveform many times to determine numeric electric amplitude values. AKA the sampling process.

Quantization – Assigning numeric values to analog signals so they can be transported over a digital network.

Pulse-code modulation – The process in which the sample (PAM) value is converted into an 8-bit, binary number.

Time-division multiplexing (TDM) – By sending data in specific time slots multiple channels of voice or data can be sent over a single connection.

Channel associated signaling (CAS) – a T1 signaling type that uses a bit from each DS0 channel to send signaling information back to the CO. Also known as Robbed Bit Signaling.

Common channel signaling (CCS) – a T1 signaling type that uses a dedicated DS0 to send signaling information back to the CO.

Robbed Bit Signaling (RBS) – See CAS steals 8th bit on every 6th frame.

Super Frame SF – Sends groups of 12 T1 frames at a time. All bits are used for synchronizing the near and far end T1 equipment.

Extended Super Frame (ESF) – Sends groups of 24 T1 frames at a time. Of the 8000 bits per second 2000 are for synchronization, 2000 for error checking and 4000 for a supervisor channel which is capable of sending control functions and error reporting.

Q.931 – ISDN CSS signaling type.

Local loop – Link between customer premises and the telco provider.

Private Branch Exchange (PBX) – customer equipment that allows them to run a private voice network.

Key system – Allows a company to run a private voice network. Usually smaller than a PBX and provides a shared line appearance. (Some new key systems may provide unique extensions like a PBX)

Signaling System 7 (SS7) – A signaling type used in the telco network to provided inter-CO connectivity and call routing.

E.164 – The ITU standard for telephone numbers and used on the PSTN.

Permanent link to this article:

Leave a Reply