==)--- P TO PAUSE S TO STOP ---(== \`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\` Basic Signaling, PT I {C} 1987 Asmodeus Rex OOTR/cDc Transcribed From 1986 Bell Tech \`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\` This is the start of a sequence of info that someof you may or may now know.. if you know it all, tell me and i will resort to something else.. Basic Signaling 4.1 General Signaling is the means used to establish and control telephone calls. It includes signals from terminals (station signaling), to and from switching centers (register signaling), and also signals between switching centers (line signaling). Signals are carried by the line and trunk transmission equipment and the switching system which convay information and commands to and from the various parts of the system and operating administration signals. The modes of signaling which will be summarized include the following types.. 4.1.1 Direct Current Signaling In the direct current signaling method (loop-disconnect signaling), a signaling code is derived from the duration and direction of the current flowing through a loop. This loop includes the customer's telephone and the line transmission equipment and it's switching center interface. Direce current loop signaling is also used with trunk transmission equipment of the wire type. An alternative methd of direct current signaling uses only one of the pair of wires and is called leg signaling 4.1.2 Alternating Current Signaling Alternating current signaling is based on signals of different frequency either in the same bandwidth (in band) as the speech transmission path (300 to 3400 Hz) or at a lower, <300 Hz, or at a higher, >3400 Hz, frequency (out band). 4.1.3 Digital Signals Digital signals take the form of a series of successive pulses, binary signals, which are coded to produce a signaling format. Digital signals may occupy a portion of one of the time slots used for the transmission of speech (in slot) or may used a dedicated time slot (our slot). 4.1.4 Signaling Path Signaling may use the same transmission path as the speech or datd signals or it may use a seperate channel. The first case is called Channel Associated Signaling, the second case Common Channel Signaling. Common Channel Signaling. Shows the principle of operating for common channel signaling. The signalin function for both line and register signaling is removed from the path carrying the transmission signals. In lieu of this a series of messages indicating the originating and terminating trunk identities, together with the relevant address or line signals, is sent over a seperate dedicated channel. This information is processed in the system controls at either end and decoded to produce the relevant actions. There are two such systems in use, or planned for use: CCITT System #6, which uses an analog signaling in band method by the use of data modems, and CCITT System #7, which uses pulse code modulation (PCM) coded signals operating at 64,000 BPS. \`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\ Basic Signaling Pt II {C} 1987 Asmodeus Rex - cDc OOTR/PAWW/MBI/MCI Transcribed From 1986 Bell \`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\ This File Was First Left On P-80, All Credit Of This File Must Be Left to P-80 When Posted On Other Systems.. - Rexxy 4.1.5 Signalin over a Carrier System The signaling path may consist of wire conductors or it may be derived from a carrier system. This provides a dedicated derived channgd from one of the 'n' inputs to one of the 'n' outputs. It uses either frequency multiplexing or pulse code modulation to multiplex the channels. 4.1.5.1 Frequency Division Carrier In the case of frequency division a number of channels are each allocated a por4ion of the bandwidth of the carrier system. Each portion is multiplexed with the carrier frequency by thE multiplexing equipment at the send end. It is demultiplexed and filtered to select the relevant channel at the recieve end to restore the speech wave form. 4.1.5.2 Pulse Code Modulation Carrier In the case of pulse code modulation a number of channels are each allocated a time slot which has a fixed recurring position in a frame of time slots. The analog input to each channel is sampled and coded at the send side and interleaved with the other time slots by the multiplexing equip. The channel is extracted at the receive en$ and demultiplexed back to analog. Signaling systems are designed for the various transmission modes and means. 4.2 Station Signaling Station signaling controls the transmission path between the terminal and the exchange and provides address information. It is used for the duration of th call. Address signaling is used to set the call up and to initiate certain kinds of services, some of which are described later on.. 4.2.1 Signals From Telephone Present-day telephones have the following signaling elements. o A hook switch which completes the loop circut when the telephone handset is lifted. This is used to originate or answer a call. Replacement of the handset opens the loop and terminates the call. o A calling device, which is either a rotary dial or a key pad. to produce the address signals, henceforth the station signals address information to the switching system center register using either dial pulses or DTMF pulses. o An alerting device, usually a bell, to indicate a call terminating on the line. 4.2.1.1 Rotary Dial The calling device which is in most common us% as The rotary dial. The rotary dial produces dial pulse (loop disconnect) signals. This calling arangement uses the standard telephone dial. rotary type, usuallt having a pulsating rate of 10 impulses per second. (IPS). However, 20 IPS dials are used in certain countrys. Dial pulsing utilizes a train of one to 10 pulses, each pulse consisting of a momentary opening of the signaling loop. The digit to be dialed is selected by rotating the dial manualy to the # selected and releasing the dial produces a requisite pulse train. The loop disconnect signals in general use, these include switch hook or equivalant signals. 4.2.1.2 Loop-Disconnect Station Signaling A calling line originates a call by a request for service signal which )s produced when the telephone handset is removed. This signal is detected by the line circut which associates a callin' device detector and a register. Dial tone is returned to the caller, who then dials the address of the requested party. The register stores the dialed units and hence accumulates the address information. The line circut register and calling device deteator respond to the following loop-disconnect signals. 'Closed Loop Signals' These can indicate a request for service or the end of a train of digits. IN the first use the signal must persist for a minimum of 10Msec. A signal occuring after request for service must persist for a minimum of 180Msec. duration to be recognized as the end of a series of pulses corresponding to a digit. (Interdigit Signal). If the signal occurs after all digits have been recieved then it is a control signal. 'Open Loop Signals' An open-loop signal can either be the beginning of a dial pulse or at the beginning of a disconnect or 'hook-switch flash' signal. If the signal is the begining of a dial pulse it will be followed by a closed loop condition within 180 Msec. If the signal is the beginning of a "hook switch flash" it will be follwed by a closed loop condition within 1 or 2 seconds. Services using "hook-switch flash" are those services which require the connection of functional units to an established call without disconnecting the established connection. Hence, depending on the class of service of the caller, a sustained open-loop condition which occurs after a closed loop must last longer than 180 Msec or 2 Sec to be recognized as a disconnect signal.. \`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\` Basic Signaling - Pt III {C} 1987 Asmodeus Rex - cDc/OOTR AEUA/MCI/MBI/PAWW Transcribed From 1986 Bell \`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\`\` 4.2.1.3 Tone Signaling from Station The advent of low-cost electronic components has made the use of key-controlled oscillators as calling devices feasible. The generic term is 'Dual Tone Multi Frequency' (DTMF). This calling device has push-button keys on the telephone innstruments which transmit two frequencies when one key is pressed. Signals are those developed by the 'Bell System' for tuch-tone service, which is a registerd trademark of Western Electric Co. Key plates in normal use have only 10 or 12 of the 16 possible keys, but some systems should be capable of responding to all 16 codes for future applications. 4.2.1.4 Registers serving lines are designed to respond to either dial pulses or DTMF signals. This uses serarate process for dial pulse and DTMF but the resulting digit (whether it was determined by counting pulses or decoding voice frequency signals) is coded in the system code (usually binary-coded decimal) and stored. 4.2.1.5 Binary Coded Decimal This coding method uses for bits per decimal digit. The first ten of the 15 possible combinations are used. The four bits have the most significant bit value (eight) on the left hand side and numbers are coded by summing the bit values; EX: Decimal value 1 is coded as 0001 and decimal value 10 is coded 1010. This method, which separately codes each decimal digit, has advantages in analyzing the digits dialed by th caller and relating them to the numbering plan. 4.2.2 Signals To Telephones The signals to the telephone of the calling party consist of tone signals, or messages, to the caller. These direct the caller's actions or advise him or her of the progress of the call. The frequencies and cadences if these tones may vary from country to country, but the CCITT is recommending the use of standard tones. This has become increasingly important with the introduction of direct international dialing. Inaddition to this there are signals which alert a caller customer. Another signal informs a customer that the telephone handset has been left of the hook, without dialing, for a predertimed period. 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