Changes

==Receiver==

==Receiver==

A ''geophone'' is a mechanical device that transforms seismic energy into electrical voltage (Figure 6). Individual geophones are often wired together and configured in arrays along a cable. These arrays are designed much the same as source arrays and for the same basic reasons, that is, to maximize detection of reflected energy and to reduce the amount of noise. However, it is important that for any geophone array to work, the individual phones must be properly planted and not just thrown out on the ground, stuck into trees, hung in bushes, or set on rocks.

[[file:seismic-data-acquisition-on-land_fig6.png|thumb|{{figure number|6}}Geophone. (Photo. Copyright: Western Atlas International.]]

[[file:seismic-data-acquisition-on-land_fig6.png|thumb|{{figure number|6}}Geophone. (Photo. Copyright: Western Atlas International.]]

A ''geophone'' is a mechanical device that transforms seismic energy into electrical voltage ([[:file:seismic-data-acquisition-on-land_fig6.png|Figure 6]]). Individual geophones are often wired together and configured in arrays along a cable. These arrays are designed much the same as source arrays and for the same basic reasons, that is, to maximize detection of reflected energy and to reduce the amount of noise. However, it is important that for any geophone array to work, the individual phones must be properly planted and not just thrown out on the ground, stuck into trees, hung in bushes, or set on rocks.

There are two basic types of cable systems: analog and telemetry. The analog systems have a pair of wires for each geophone group and several additional pairs of wires for roll-along. (Roll-along allows for shooting to continue while geophones are picked up behind the shot and moved into position in front of the shot.) For example, a 96-channel system may have 72 pairs of wires for the front part of the cable and the same for the back. Likewise a 240-channel system may have as many as 144 pairs of wires. The advantage to this sort of hard-wired system is that it can be used in most any type of terrain. However, if these cables get too long, the signal may be attenuated by leakage or obliterated by 60-Hz noise. These problems can be overcome by telemetry systems (also known as distributed systems), which have an analog connection from the geophone group to a processor. The processor or station box amplifies the analog signal, filters, digitizes, and transmits the digital signal to the recording facility by wire, optical fiber, or radio. Hybrids of these two systems can be used to accommodate varying field conditions.

There are two basic types of cable systems: analog and telemetry. The analog systems have a pair of wires for each geophone group and several additional pairs of wires for roll-along. (Roll-along allows for shooting to continue while geophones are picked up behind the shot and moved into position in front of the shot.) For example, a 96-channel system may have 72 pairs of wires for the front part of the cable and the same for the back. Likewise a 240-channel system may have as many as 144 pairs of wires. The advantage to this sort of hard-wired system is that it can be used in most any type of terrain. However, if these cables get too long, the signal may be attenuated by leakage or obliterated by 60-Hz noise. These problems can be overcome by telemetry systems (also known as distributed systems), which have an analog connection from the geophone group to a processor. The processor or station box amplifies the analog signal, filters, digitizes, and transmits the digital signal to the recording facility by wire, optical fiber, or radio. Hybrids of these two systems can be used to accommodate varying field conditions.