Category Archives: Circuits & Signalling

Signalling and Call set-up There are three types of Signalling: 1) Supervisory: On-hook, off-hook, Ringing 2) Address: Communicates the digits that were dialed like DTMF (Dual tome multi frequency) and Pulse dialing 3)Informational: Dial-tone, ring-back tone, recorder tone. Call set-up: 1.The calling phone goes off-hook, closing the circuit to the local CO switch. 2. TheContinue reading “Signalling & Call Set-up”

T1 Cicruits: Each T1 circuit consits of 24 channels. Each channel is capable of holding one voice call of 64kbps. If there are not enough voice calls then the gaps are padded with null values. The 24 channels are grouped in a frame. It depends whether it is SF (i.e. frame of 12 channels) orContinue reading “Circuits and Signalling”