Patent GB-940016-A (GB)
Title: Improvements in or relating to automatic telecommunication systems
Inventor: HARRIS LIONEL ROY FRANK
IPC: H04Q11/04
Filed: 1959-10-26
Abstract: 940,016. Automatic exchange systems. POSTMASTER GENERAL, STANDARD TELEPHONES & CABLES Ltd., GENERAL ELECTRIC CO. Ltd., AUTOMATIC TELEPHONE & ELECTRIC CO. Ltd., ASSOCIATED ELECTRICAL INDUSTRIES Ltd., and ERICSSON TELEPHONES Ltd. Oct. 26, 1960 [Oct. 26, 1959], Nos. 36168/59 and 17861/60. Heading H4K. The Specification describes an electronic exchange having the following features :- (a) The relation of the lines to the connecting devices is on a basis different from the local portions of the directory code numbers, and registers common to all the lines, receive the directory numbers from the calling subscribers and transmit the local portion thereof to a code translator common to all the registers for translation into an equipment number so that a change in the directory number of any local line can be made in the code translator. (b) A central storage device is provided for maintaining, for all calls, a continuous record throughout the call of the state of progress of the call, with means for detecting changes in the state of the call and signalling them to the storage device. (c) Observation operators are provided with the facility for setting up observation connections to any line. This facility may include means for breaking in upon an existing connection. Speech transmission.-The subscribers are divided into four groups of 800 lines. Each group has an inspeech and an outspeech highway each carrying 100 time division multiplex channels, each channel consisting of a ¢ Ásec. pulse recurring at 100 Ásec. intervals. For a given connection the inspeech and outspeech channels are 50 Ásec. out of phase. Normally, the pulse allotted to the called-calling direction is referred to as the P pulse and the pulse for the reverse direction as the P+50 pulse. Each highway is associated with fifteen 100 Ásec. delay line stores comprising 3 groups of 5 stores XA ... XD, YA ... YD, ZA . . . ZD, each subscriber being associated with 2 stores in each group. A called subscriber is connected to the group in speech highway by inserting a P pulse into his appropriate combination of stores whose outputs are combined to enable a line modulator to pass speech modulated pulses to the highway. Each store has a centre tap providing a P+50 output, such outputs being similarly combined to enable a demodulator to pass signals on the outspeech highway to the called subscriber. In the calling subscriber group similar operations take place with the exception that a P+50 pulse is inserted in the store for inspeech and the centre tap P pulse is used for outspeech. To complete the connection, each inspeech highway is connected via gates to the outspeech highway of every other group and vice versa. Thus each group m is associated with four intergroup stores Dn/m (n=1 ... 4) which enable gates between the inspeech highway of group n and the outspeech highway of group m. Thus, if n is the called group and m is the calling group, the P pulse is inserted in Dn/m and the P+50 pulse is inserted in Dm/n. Tone transmission and line split.-Each group has four 100 Ásec.centre tapped tone stores A ... D. When a tone is to be sent the appropriate outspeech pulse is inserted in two of the stores (NU tone - AB; Busy tone - AC; Dial tone - BC; Tone Ringer - CD). The P+50 outputs from this store combination enable a modulator fed with the appropriate tone and pulses modulated with this tone are fed to the appropriate highway. Pulses in store D close a gate to disconnect any other input to this highway to provide " line split " in the case of Tone Ringer. Line split can also be provided without sending any tone by putting the pulse in store D only. Temporary information.-Information concerning the state of lines is stored on " operate tracks" of a magnetic drum in positions appropriate to the line. Information concerning the state of a call is stored in the " supervisory " in circulating stores comprising delay lines 900 Ásec. long. Supervisory.-900 time positions are used to store information about calls in progress, the time position being the 1 in 100 Ásec. channel time position in use gated by one of nine 1 Ásec. pulses GP1 ... GP9 having a recurrence period of 9 Ásec. Thus a pulse in any of the stores indicates the outspeed (1 in 100) pulse position of the subscriber in question and his group by means of the GP position. The supervisory comprises :- (a) Four stores various combinations of which indicate various states of call for the subscriber whose pulse is circulating therein; the states indicated are a 1 -subscriber calling, a 2 -calling subscriber has been answered, a 3 - calling subscriber has been ansered and called subscriber has cleared, b 1  called subscriber being run, b 2  called subscriber has answered, b 3  called outgoing junction being held during a " junction guard " period. (b) Four stores to indicate the class of the line in question, e.g. ordinary or X party subscriber, Y party subscriber, PBX line, junction line. (c) Three stores for use in metering. (d) One store for use in persistence testing, i.e. whenever a line changes its condition (e.g. called party answers or clears, or calling party clears) a test is made to ensure that the change of state persists for the 160 ms. interval between two S pulses. During the first S pulse after the change of condition, a pulse is inserted in the store and in the interval between this and the second S pulse numerous opportunities are given for deletion of this pulse should the line have reverted to its original condition in the meantime. If the pulse is retained until the second S pulse then it is released to perform its appropriate functions. (e) Two stores for use in time out operations, Signalling between supervisory and group equipment.-Pulse signals sent from 100 Ásec. equipment associated with groups to the supervisory pass through gates opened by the appropriate GP1 ... GP9 pulse to provide the 1 in 900 Ásec. signal required. 1 in 900 Ásec. signals from the supervisory are when necessary applied in parallel to gates associated with the inputs of 100 Ásec. group stores. GP1 ... GP9 pulses also applied to these gates ensure that only the store of the group concerned receives the pulse. Intergroup path.-The supervisory may apply the I in 900 Ásec. identity of a channel and its group and to obtain the 1 in 900 Ásec. identity (50 channels out of phase) of the channel and its group to which it is connected. Each group contains a centre tapped 100 Ásec. intergroup path store. When the supervisory emits a 1 in 900 Ásec. pulse P it is gated by the appropriate GP pulse into the intergroup store in question, say that of group m, and circulates therein for 900 Ásec. P+50 pulses are taken from the store and compared with the outputs from the intergroup stores Dm/n (n=1 ... 4) in gates which are also pulsed with the GP pulses appropriate to the n groups. As a result one gate is opened for a particular value of n and a 1 in 900 Ásec. P+50 pulse is emitted. This is returned over the return intergroup path lead for use in the supervisory. The intergroup path has an auxiliary use. A pulse inserted in the intergroup path store during an x 3 interval (see Fig. 47) and therefore emitted during x ¥  is used in its P phase to clear the associated line stores of the pulse in question, thus disconnecting a subscriber using this phase from his highways. The magnetic drum. Main library tracks.- The drum contains, inter alia, 32 tracks each containing 100 words each of 28 bits (TA1 ... TA28). Each word is associated with a line equipment number. The first 16 bits contain the line equipment number in binary form and the remainder of the word is used for class of service information. Timing circuits associated with the drum emit pulses in the TA1 . . . TA28 position for each word. A group of 5 leads XA ... XE is pulsed in different combinations of 2 out of 5 successive words. A further group of 5 leads YA ... YE is also pulses in 2 out of 5 combinations for successive groups of ten words. A complete cycle XA ... XE/ YA ... YE thus occurs during 100 words, i.e. one revolution of the drum and the combination of these leads thus identifies the position of a word within the 100 on the track. In 10 revolutions of the drum (8 of which are used) which are indicated by 2 out of 5 combinations of leads ZA ... ZE all eight tracks appropriate to a subgroup of 800 lines may therefore be indicated. Two groups of ZA ... ZE leads are provided, one for supervisory scanning and the other for initial line scanning. " Operate tracks."-These are used to store temporary information concerning a line, e.g. " busy," " park," " 5K," " line fault," " call trace " and " conditional busy," all of which will be explained later. 7 bits per line are required for this information. Two tracks per group are provided. Each word position TA1 ... TA28 corresponds to a word in the main library track having the same XA ... XE/YA ... YE code, but the word is divided into four sub-words TA1 ...TA7, TA8 ... TA14, TA15 ... TA21, TA22 ... TA28 which are used respectively for lines in four subgroups so that the eight sub-groups are accommodated on two tracks. Each sub-word is provided with its own set of writing and reading circuits, there being in each set triggers set by the output from appropriate bits, triggers whose outputs are read on to the tracks at the appropriate bit time, and intervening circuitry for changing the record on the track as circumstances demand. Information is thus always available from the appropriate triggers regarding the state of any line. Signalling.-Each group has an insignalling and outsignalling highway carrying pulses synchronous with those on the inspeech and outspeech highways respectively. The insignalling highway carries various information concerning the line which cannot conveniently be stored in the class of service information on the drum, and also certain instructions which may be