Patent GB-921834-A (GB)
Title: Delayed call telephone system
IPC: H04M3/523
Filed: 1960-10-07
Abstract: 921,834. Automatic exchange systems. STANDARD TELEPHONES & CABLES Ltd. Oct. 7, 1960 [Oct. 9, 1959], No. 34398/60. Class 40 (4). [Also in Group XL (c)] In a telephone system which includes equipment having limited traffic capcity, particulars of calls awaiting completion are recorded and an idle channel is allotted to that call of the highest priority having the oldest filing time. As described the limited capacity equipment includes radio links between ground stations which are routed via intermediate stations situated on 24-satellites orbiting the earth. It is assumed that eight ground stations are each allotted twelve transmit channels and that each may receive the eighty-four channels on which the others transmit. The individually allotted subcarrier frequencies of the ground station transmit channels are linearly added at the satellite, the resulting frequency multiplexed signal being amplified, shifted to new frequencies, and re-broadcast to all ground stations " seen " by the satellite. At each ground station the priority, calling and called numbers and time of each call extended thereto for completion via the limited capacity equipment are recorded. Each time a transmit channel becomes idle, all locally stored such data is scanned and that of the highest priority call having the oldest filing time is read out and is transmitted over the channel. Each ground station thus receives data relating to calls queued at other ground stations and data relating to calls queued locally: it compares the data and assigns idle channels to the call of highest priority having the oldest filing time of all calls awaiting switching at the ground station concerned. Local data storage.-Calls incoming over local two-way trunk 10 (Fig. 2) are extended by access switch 20 to local register 21 which stores temporarily impulse trains indicative of the priority of the call and the calling and called numbers. This information is also displayed at an operator's position 12 in order that an operator may supervise person-toperson calls or challenge the priority claimed. The information in register 21 is transferred via access switch 30 to semi-permanent storage 31 which calls in clock and calendar 40 for recording the filing time and day. Local register 21 is released and access switch 20 steps on to the next calling trunk. On instructions from the operator, the caller hangs up. Read-out.-With information stored in circuit 31, marker 33 tests for an idle channel and on finding one causes the scanner 32 to select from circuit 31 the call having the highest priority and oldest filing time. The multi-frequency sender 41, driven from oscillator 75, reads out the called area code, priority and filing time of this call, and this information is pulse-code modulated at 52 for transmission by transmitter 53 and antenna 54. At any other ground station having pending calls a similar process is effected, and at each station the information received over antenna 54 from other stations is demodulated at 63, fed to multi-frequency receiver 64 and thence to temporary storage in incoming register 61. It is then transferred via access switch 72 to incoming call storage 71. The incoming scanner 70 selects from storage 71 the highest priority call having the oldest filing time and marker 33 compares the data for this call with that of the selected local call to determine which is to have preference. Local call.-Assuming that the local call is chosen, the marker causes outgoing selector 23 to seize junctor 13 associated with the idle transmit channel, which junctor splits, connecting the marker 33 to the transmitter 53 and terminating the two-way trunk circuit 10 to prevent singing. The sender 41 transmits the call data over the channel and causes it to be displayed at operator position 12 for the duration of the call. The junctor 13 is then switched through, whereafter marker 33, local storage scanner 32, incoming scanner 70, outgoing selector 23 and sender 41 are released. Request for channel assignment.-At the called ground station the data is stored in incoming register 61 which retains only data in respect of calls for its own area and transfer it to storage 71. If a transmit channel is idle a reply is sent to the calling station to signal assignment of a receiving channel; if not a free channel is awaited. When a channel is free, marker 33 at the called station is connected by scanner 72 to incoming storage 71 and by scanner 32 to local storage 31 and determines which call is to have preference. If it is the incoming one, the marker sets the incoming selector 60 to interconnect the idle transmit channel and the awaiting receive channel, and operates outgoing selector 23 to seize the associated junctor 13. The sender 41 transmits the information read out from marker 33 and releases. At the originating centre the marker 33 sets selector 60 to interconnect the two channels concerned and the operator is signalled that this has been done. The reestablished connection with the caller via conventional equipment, and keys the wanted number, in response to which register 61 at the called station calls in sender 73 which set up a connection to the wanted party via local selector 11 and a free trunk 10. High priority calls.-If a high priority call is waiting the incoming storage 71 signals the operator position 12, whereupon the operator interrupts a low priority call and tells the parties to conclude their conversation. Thereafter, a timer measures a given period, whereupon the operator takes down the connection and sets up the high priority call over the channel thus released. Specification 921,835 is referred to.