Status of the Networks in the Klerksdorp Area, June 1997

Abstract

Implementation of the long-term plan for 1996–1998, as decided in 1994, was based on results of actions taken in 1994–1995.

Appendix 5.1 Technical Description of the Klerksdorp Networks (Status End of 1997)

5.1.1 KMMA Regional Seismic Network

The Regional Network (Fig. 5.9) consisted of a RTS (Run Time System), a Silicon Graphics computer, a Network Multiplexer, and a PC-based system with multiple serial ports. Outgoing data was transmitted directly from the communication ports on the RTS system, and all incoming data was received via the Network Multiplexer. Communication between the RTS and the Network Multiplexer took place by means of an Ethernet network (10BaseT). The outgoing data was transmitted by transmitter 1 at 150 b/s, and incoming data was received at 1200 b/s (baud).

Fig. 5.9

KMMA Regional Seismic Network

The network multiplexer consisted of a PC-based system with a 64 RS-232 ports. These ports were fully software controlled and could be reconfigured by the RTS while receiving and transmitting on a different baud rate (150–19,200 b/s). The network multiplexer was connected to a second FOS unit via two fibre-optic cables in full duplex mode. This fibre- optic connection insured full electrical isolation between the RTS, network multiplexer, and the radios. From the second FOS unit, a RS-232 line connected it to the transmitting modem. This modem converted the RS-232 data to frequency-shift keying (FSK) format and passed it to the UHF Radio transmitter 1 (449,300 MHz). The frequencies used by the logic 0 or 1 were respectively 390 and 490 Hz.

At the shaft headgear, a radio receiver passed the FSK data on to the hybrid. The hybrid was connected to the underground site with a single pair of telephone wires. The function of the hybrid was to superimpose the receiving data (from the RTS) and the transmitting data from the IS, PS, or MS on one telephone line. At the underground site, the seismometer could be an Intelligent Seismometer (IS), Processing Seismometer (PS), or a Multi-Seismometer (MS). The data was transmitted at 1200 b/s in a FSK format, and the two carrier frequencies were 1200 hand 2400 Hz, respectively. The data from the underground site to the RTS followed the same line to the hybrid, then to a separate radio transmitter. At the central site , a radio receiver or a direct telephone line passed the data to a modem, which converted the FSK to RS-232 format. The incoming data was channelled to the FOS unit on receiving ports (RS-232). This means that 55 serial ports were communicating with the RTS at any one time. A time update was sent to all seismometers every five minutes via transmitter 1.

5.1.2 The No. 5 Shaft 5B Seismic Sub-network (As It Was Until June 1997)

The 5B sub-network (Fig. 5.10) was originally part of the regional network, but, due to the low data rate of 150 b/s, the transmitted data from all the stations became too much and we were forced to split the two networks. Both were still transmitting at 150 b/s. All the communications that were relevant to all the stations in the No. 5 Shaft area were channelled to a separate port and transmitted trough the FOS units to a modem (converting the RS-232/FSK) and then to the radio transmitter (transmitter 2). On the shaft side, a radio receiver passed the incoming data to a multiplexer, which sent the data to all eight processing seismometers. The processing seismometer sent the outgoing data 1200 b/s in FSK (1200 and 2200 Hz) format to the multiplexer. The function of a multiplexer was to compress the outgoing data from a number of stations in a network into a single communication link. The data was transmitted in FSK format at 9600 b/s to a modem on the surface. This modem converted the FSK data to RS-232 and passed it on to a T-modem, which was a high-speed intelligent radio modem, capable of 9600-b/s-data transmission using GMSK modulation.

Fig. 5.10

No. 5 Shaft 5B area seismic sub-network

At the office site, a T-modem received the data (converting the GMSK to RS-232) and passed it on to a channel in the FOS unit through the fibro cable to the network multiplexer into the RTS. There was a time update to the stations every five minutes. This network in June 1997 was upgraded to 2400 b/s.

5.1.3 No. 1 Shaft Vaal Reefs Seismic Sub-network

The No. 1 Shaft sub-network (Fig. 5.11) was a part of the Regional Klerksdorp Network. This sub-network consisted of only four stations with a multiplexer (the other two stations were in the Regional Seismic Network). The RTS communicated through the SCSI terminal server (serial port) to a line modem. This network used only one telephone line and no radio receivers or transmitters. The transmission from the modem to the multiplexer was the normal 150 b/s (FSK format). The data was then distributed to all the stations (PSs) via the multiplexer. From the stations, the data (FSK format) was passed to the multiplexer, which compressed the data onto a single line but at 9600 b/s. This was passed on to a receiving modem at the office side. The data was converted to RS-232 format by the modem and connected to a separate channel on the FOS unit. The received data flowed from the FOS unit via the network multiplexer to the RTS. The time update to the stations was transmitted every five minutes.

Fig. 5.11

No. 1 Shaft Vaal Reefs seismic sub-network

5.1.4 The No. 4 Shaft and No. 2 Shaft Hartebeestfonte in Sub-networks

With the experience from the previous three networks, it became clear that the data transmitted at 150 b/s was too slow for the number of stations linked to the RTS . The bottleneck of the system seemed to be the radios. With the modulation spacing of 12.5 kHz, a new modulation technique had to be implemented to achieve a higher transmission rate through the radio transmitters. It was decided to go for the FFSK (fast-frequency shift keying). The No. 4 Shaft Hartebeestfontein sub-network (Fig. 5.12) was the first network to run on this new technology. If this technique would prove itself, it was planned that the Regional Klerksdorp Network would also be converted to 2400 b/s. The 5B sub-network at that time was in the process of being extended to 15 stations working on 2400 b/s from the RTS. Data was transmitted at 2400 b/s from the RTS through the SCSI terminal server to the network multiplexer to a FFSK modem (1200 and 2400 Hz) and then to a radio transmitter (3).

Fig. 5.12

No. 4 and No. 2 Shaft Hartebeestfontein sub-networks

In the shaft area , a radio receiver received the incoming data from the RTS and channelled it to the hybrid. The hybrid converted the FFSK (1200 and 2400 Hz) data at 2400 b/s to FSK (2500 and 4500 Hz) data at 2400 b/s, and then sent it to the underground multiplexer. From the multiplexer, the data then passed to all the stations (MS) on a single telephone line. From the stations the data was transmitted at 2400 b/s (16,000 and 24,000 Hz) to the multiplexer. The multiplexer compressed the data to 9600 b/s and transmitted it to the T-Modem at the shaft headgear. At the central site, a T-Modem received the data, converted it to RS-232 format, and passed it on to the FOS unit, then to the network multiplexer on a separate channel. The time update was also sent every five minutes to the stations.

5.1.5 The No. 8 and No. 11 Shaft Vaal Reefs Sub-networks

The RTS sent the outgoing data to the network multiplexer via an optic cable. The network multiplexer consisted of a 486/33 MHz PC and three smaller FOS units. These FOS units communicated via separate fibre-optic cables (two pair per multiplexer) to the three multiplexers underground. From the multiplexers data was sent in FSK format at 9600 b/s to every outstation. Data from the stations was sent at 9600 b/s to the multiplexers. This data was then passed on to the network multiplexer and then to the RTS . To process the data from these networks, a fibre-optic link was used between No. 8 Shaft and the central site (Fig. 5.13).

Fig. 5.13

No. 8 and No. 11 Vaal Reefs Shafts seismic networks

5.1.6 The No. 2 Shaft Vaal Reefs Sub-network

This network (Fig. 5.14) had its own RTS on the shaft. For the processors to process the data, a radio LAN (microwave link) was installed on the shaft headgear. A fibre-optic cable and media converters between the headgear and RTS assured a one Mb/s data-transfer speed between the seismic offices and the RTS. The RTS on the shaft sent the data and time- update pulse (RS-232 150 b/s) via the serial port of the Silicon Graphics computer to a modem, which converted the RS-232 to FSK format and passed the data on to the three multiplexers. The multiplexers passed all incoming data and time-update pulses to the stations. The stations sent their outgoing data at a rate of 1200 b/s also in FSK format to the multiplexers. The multiplexers compressed the received data to 9600 b/s and converted it to RS-232 format and then passed it on to the eight-channel SCSI terminal server. Each multiplexer used a separate channel. A 50-pair cable was installed down the shaft from the surface to the 74 level. At the time, it was planned to convert this network to 2400 b/s with a single multiplexer and 24 channels.

Fig. 5.14

No. 2 Shaft Vaal Reefs sub-network

5.1.7 The No. 4 Shaft Vaal Reefs Sub-network

During the second half of 1997, this network (Fig. 5.15) was in the process of being installed. When completed, it would consist of eight stations and a RTS on the shaft. The data from the RTS would be transmitted through a radio LAN to the offices for processing. A high-speed, short-range modem (V.11 RS-422) would provide the data transfer between the RTS and the underground multiplexer. The data flow between the multiplexer and the stations could be either 2400 b/s for a single-pair cable or 9600 b/s for a two-pair cable installation. An optical fibre and media converters would be installed between the RTS and the shaft headgear, where the radio LAN would operate. The geophone boats would be equipped with SM14 (14 Hz) geophones.

Fig. 5.15

No. 4 Shaft Vaal Reefs seismic network

5.1.8 The No. 5 Shaft Vaal Reefs Pillar Network

A 16-port serial SCSI terminal server interfaced the RTS with a V.11/RS-422 modem. Data was sent from the RTS via the asynchronous V.11/RS-422 short-range modem to the multiplexer underground at a speed of 9600 b/s. With a two-pair signal cable from the multiplexer to an outstation, it was possible to send and receive the data at a rate of 9600 b/s. The processors accessed the data on the RTS through a radio LAN link. This network was generating its own time update (Fig. 5.16).

Fig. 5.16

No. 5 Shaft Vaal Reefs pillar seismic network

5.1.9 The No. 5 Shaft Vaal Reefs Upgraded Network

This network (Fig. 5.17) operated in the same way as the No. 2 Shaft and No. 4 Shaft Hartebeestfontein networks. The only difference between them was the data link from the multiplexer to the RTS. The stations received data at 2400 b/s and also transmitted data at 2400 b/s. A high-speed modem transmitted the data from the multiplexer to the RTS through five km of telephone lines.

Fig. 5.17

Vaal Reefs No. 5 Shaft upgraded seismic network

5.1.10 KMMA Regional Seismic Network Surface Site

Figure 5.18 illustrates one of the surface geophone sites. These stations were located in the felt far away of any centres of human activity , even the smallest-possible ones. Once they were detected, they were vandalised on a regular basis. For this reason, we had to secure them as well as possible. Solar panels had to be installed on top of 12-m-high steel constructions. Still, the robbers would climb up them and take the panels. The next security upgrade would include anti-climber barbed wire on the poles. Still, some of the solar panels were stolen.

Fig. 5.18

Surface site