CS-430 is the Underground family's emplaced passive seismic and acoustic node. Seated at a surveyed position and spliced into a buried fibre, it neither moves nor transmits again. It receives, and reports on a wire.
A buried instrument restated as a fleet node: a sealed body couples a passive sensor to the ground, an ultra-low-power stack sleeps behind an analog wake-up, and a dark fibre carries the record out.
A sealed cylindrical housing in moulded polymer, direct-buried or augered in: pressure vessel, corrosion barrier and first element of the signal chain at once.
A tri-axial geophone and a MEMS accelerometer read ground-borne vibration; an acoustic sensor reads what travels through air and structure. Every element is passive.
Fibre only, node to node or straight to a head-end, in a daisy-chain line. Emissions over the air are none, in any wake state or configuration.
The sequence is short. The position is surveyed, the node is augered or hand-buried and seated at depth, the fibre lead is spliced into the head-end or the next node down the chain, and the pit closes. After that it does nothing visible for a very long time: sleep and listen, wake on a threshold, classify locally, report once, sleep again.
It has two lives. Strung node to node on a fibre trunk, a run of them is the Trembler Line CS-435. Emplaced alone, one node is a listening post over an approach nobody else has eyes on. Its family is Underground.
Deployment is the only kinematics in the node's life cycle. There is no drive, no propulsion and no locomotion on the platform, and each of the three substitutions below is harder than what it replaces.
What is left is one question asked over a very long time: does the sensor hear the ground, or a gap? On a line the same node is three things at once — the detection element, a fibre relay for its neighbours, and the surveyed reference the solution is computed against.
Half of the coupling subsystem is hardware and half is procedure, and the procedure is engineering rather than an afterthought. A poor install is not recoverable afterwards.
A buried case on soil is a sprung mass. Its coupling resonance rises with soil contact stiffness and falls with node mass, and it has to sit clear above the band the node listens in, or the mounting rings inside the signals the node is there to read. Two rules follow: seat the feature in undisturbed soil, and keep the node modest in mass. Loose backfill is the classic failure, lowering the stiffness, dropping the resonance into the band, and colouring everything the node reports thereafter.
Coupling is time-varying too: saturation and freeze-gap formation change the contact stiffness across seasons, and a drift shows up as a shift in the ambient spectrum the node reports long before it shows up as a missed event.
| Coupling feature | Where it suits | What it buys |
|---|---|---|
| Spike or cone | Undisturbed soil at the bottom of the hole | The simplest hand-emplaceable seating, and the highest stiffness for the least work |
| Base plate | Soft or organic ground | Bearing area where a spike would sink rather than seat |
| Full burial, compacted or grouted | Permanent installations | The ground itself clamps the case, and the other two are measured against it |
One mount carries all three. Inside, a rigid chassis ties the sensing element onto the coupling feature by a short, stiff, glue-free load path, because any give in that path subtracts signal.
Burial depth is 0.3–1.0 m nominal and site-dependent, a per-site output rather than a catalogue figure. Depth buys three things at once.
Seasonal stability comes first: below the frost line the node sits at near-constant temperature and stress, close to ideal storage for the battery, where above it every freeze-thaw cycle re-works the seating. Second, surface-noise rejection, because wind, rain and traffic couple most strongly into the uppermost soil. Third, concealment.
Auger or post-hole to depth, seat the coupling feature in undisturbed soil at the bottom, backfill in compacted lifts, dress flush. The cheapest and best-controlled coupling there is; it asks for someone to walk the line.
Node and node-to-node fibre laid in one shallow trench pass, so emplacement and network build are one operation. The natural mode for a planned line on owned or permitted ground.
The node travels down a CS-410 tube bore and is emplaced at the head, the fibre handed back out through the bore. No surface signature along the line.
Mode C is what makes the family a family. CS-410 and Aquifer CS-411 make holes; this node, CS-425 and CS-460 work holes that already exist. A node near a bored conduit can draw from a line supply on the optional tether-tap.
Deploy-and-forget is an energy claim before it is anything else, and it rests on three rules: the sensor is free, the wake-up is analog, and the fibre is dark.
| State | What is powered | Power class | Exit |
|---|---|---|---|
| Listen · the default | The geophone at 0 W, the analog threshold front end and the clock | ~10–100 µW | A threshold crossing, a health timer, or wake-on-light from a neighbour |
| Capture | Converter and processor: sample, timestamp, feature-extract, classify | ~10–50 mW, seconds | Event closed and scored |
| Report | The optical transceiver: burst the event record up-line, relay neighbours' traffic | ~50–150 mW, seconds | Acknowledgement from the line |
| Health | Battery voltage under load, a coupling-spectrum snapshot, the moisture telltale | Report class, ~once a day | Timer |
The node spends effectively all its life in the first row, three orders of magnitude below the third.
A moving-coil geophone is a generator, not a consumer: it draws nothing and puts out a signal proportional to ground velocity, so the sensor costs nothing to leave switched on for years. That moves the whole design onto the wake-up, which has to be an analog comparator chain on the geophone output. A digital sampler that never stops sampling is already in the third row, and a node that lives in the third row does not get left in the ground.
The events are almost free. Take a busy site at 20 events/day, each 10 s of Capture at 50 mW and 2 s of Report at 100 mW: capture 10 J/day, report 4 J/day, one daily health report about 0.5 J. That is 14.5 J/day, an average of ~0.17 mW. Endurance is an outcome of the electronics architecture rather than of battery size, and bigger cells cannot rescue a design that wastes milliwatts.
The third rule follows from the same arithmetic. Conventional optical transceivers idle at tens of milliwatts, so the link is dark by default and energized only to report or relay, with a wake-on-light receiver at microwatt cost. Hold both disciplines and the node reaches the end of its calendar life or of its seal rather than the end of its energy. The pack is primary lithium of the long-shelf-life class; standby endurance is the years class at ultra-low duty cycle.
The fleet's one-envelope, many-payloads discipline, in passive form: one sealed, coupled, fibre-linked body, and four ways to fill it, every one of them listening only.
A single vertical-axis moving-coil geophone, the workhorse of a century of seismic practice, drawing 0 W. It hears that something is happening, and roughly how energetically, for microwatts.
A tri-axial set buys polarization and a single-node back-azimuth, so a line solves position from arrival times and bearings rather than times alone, at the same node count.
Fitted where a node sits near a tunnel, culvert or pipeline. Seismic and acoustic together separate source types: an engine in a void is acoustic-strong and seismic-weak, digging the reverse.
Pipeline leak and third-party-interference monitoring, and slope and seismic monitoring: leak noise and an excavator strike are the same detection problem on the same hardware.
The natural line is mixed: bearing-variant anchor nodes among cheaper baseline pickets, in a proportion the survey settles. Every variant shares the mount, the envelope, the power stack and the link, so a new element is tooling rather than a redesign.
What is absent is absent by rule, in every variant and for every customer. No active seismic sources, no acoustic projectors, no electromagnetic emitters, and no effector content of any kind.
The body holds out soil pressure, groundwater, freeze-thaw and soil chemistry for a very long time, and passes ground motion to the sensor with as little colouration as it can while doing it.
Moulded glass-filled nylon is close to ideal for the duty: no corrosion, no galvanic couples, electrically inert, mouldable on the group's own tooling. There is no radio aboard to shield, so the one property a polymer case normally costs is not one this node needs.
The case carries four jobs. It excludes water at sustained hydrostatic head, and because burial below the water table is assumed the seal specification is a submersion specification rather than a splash rating. It resists soil overburden and frost-heave loads without cracking. It carries the coupling feature, and presents a service interface that preserves the seal.
Inside, a rigid chassis mounts the sensing element straight onto that coupling feature, and the battery sits low and hard, where its inertia works for the coupling rather than against it. The electronics are conformally coated and potted against the condensation decades of thermal cycling produce in any sealed volume, and a desiccant and a moisture telltale share the space with them — the telltale readable over the fibre, a near-free health measure on a node nobody is going to open. Operating temperature is the −40 °C to +50 °C class.
Footsteps and digging read at tens of metres, vehicles farther and soil-dependent. Any detection-range figure states its soil and threat class.
Ground-borne amplitude falls with distance twice over, by geometric spreading and again by absorption in the material it travels through. High frequencies die first, so the useful band collapses toward low frequency as range grows. Source strengths span orders of magnitude between a footstep, hand-digging, mechanized tunnelling and a vehicle, and a site's noise floor spans orders of magnitude again.
Two consequences follow, and both are commercial. Node spacing is an output of the site survey, so a line is delivered as a surveyed, commissioned system rather than as nodes at a fixed interval. And discrimination is done at the node: the threshold detector rejects wind, weather and passing wildlife, and catches digging, footsteps, vehicles and tunnelling.
The fleet's rule is that the link is the vulnerability. No Canadian Shield design transmits by radio and none guides on a link, and this node is where the rule reaches its cleanest expression.
Once the fibre is spliced and the pit is closed, the node emits nothing over the air in any wake state or configuration: not a beacon, not a heartbeat, not a status ping. There is nothing to intercept because nothing is sent, no receiver to jam, and no satellite fix to lose or spoof — the node knows where it is from the survey that put it there. Two glands carry the dark fibre in and out, and they are its only ports.
No emitter and no designator of any kind: no active seismic source, no acoustic projector, no electromagnetic emitter. A passive sensing node with no warhead, no fuze and no energetic material, and no offensive capability of any kind. Its output stops at data on a fibre.
Human safety runs first across the fleet, and here it is the product rather than a constraint on it. Every hour a node keeps watch on a chokepoint is an hour nobody had to stand a post there. The fleet's rules are on the doctrine page.
A line's solution is only ever as good as the node survey behind it, so what a node learns about itself at install is part of what is bought.
Tilt comes free, from a static read of the accelerometer at commissioning. Absolute azimuth, which the bearing variant needs, comes from the install-time survey where the surface is worked, and from a known-source calibration thump at a surveyed point where the node went down a bore. The thump doubles as the acceptance test, and it matters because coupling quality cannot be recovered afterwards: it is accepted on the day or carried for the life of the node.
There is no link check to run. The link is a wire, and it is either spliced or it is not. What follows is the scheduled self-check on its slow cadence, and a detection latency short by comparison — a sub-second threshold trip, and a report to head-end under 1 s over fibre.
One table, and the ground the node is buried in decides most of it.
| Item | CS-430 |
|---|---|
| Configuration | Sealed cylindrical housing, direct-buried or augered in |
| Housing dimensions | ~90 mm dia × ~380 mm length |
| All-up mass | ~4.5 kg |
| Sensor package | Tri-axial geophone · MEMS accelerometer · acoustic sensor |
| Detection range | Footsteps and digging — tens of metres; vehicles — farther, soil-dependent |
| Wake and report latency | Sub-second threshold trip; report to head-end under 1 s over fibre |
| Comms | Buried fibre only, node-to-node or direct to head-end — no radio |
| Emissions over the air | None, in any wake state or configuration |
| Battery chemistry | Primary lithium, long-shelf-life cell class |
| Standby endurance | Years-class at ultra-low duty cycle |
| Burial depth | 0.3–1.0 m nominal, site-dependent |
| Operating temperature | −40 °C to +50 °C class |
| Recovery | Dug back along its own fibre lead — or logged and left in place by decision |
| Payload | None — sensing electronics and battery only |
| Munitions classification | Passive sensing node — no warhead, no fuze, no energetic material; no offensive capability |
| Chain role | Node of the Trembler Line CS-435 picket; also emplaced standalone as a listening post |
Any detection-range figure states its soil and threat class. Every design in the family is patent pending, and international transfer is export-controlled and subject to Canadian government permits.
Strung node to node on a fibre trunk back to one monitored head-end, a run of CS-430 nodes becomes the Trembler Line CS-435.
The chain detects, localizes and cues, and the cue goes to a person at a console rather than to a machine. Where a confirmed cue calls for a physical response, that response is CS-425 sent forward to interpose on a human decision. This node's role ends at data on a wire; it commands nothing, and no strike authority exists in the loop to command.
A single node does not need the chain to be worth having, and the two are sold as different things. The chain and what a commissioned line delivers are on the Trembler Line CS-435 page; the buyer's view of the family is who it is for.
It suits a buyer who owns ground, or a line under someone else's. It is not built for a buyer looking for a weapon.
If you hold a chokepoint, a perimeter or a line under ground you do not own, the conversation starts with the node that does the listening.
A screened enquiry opens it, never a quotation. Bring the ground, the approach and what a detection there would have to set in motion. Canadian Shield brings the node, the coupling and the line it strings into. Counsel comes first on any international transfer, and permits are taken per shipment.
The Underground family is the six programs side by side, and the Trembler Line CS-435 is what a run of these nodes becomes.
All Underground family designs are patent pending; international transfer is export-controlled and subject to Canadian government permits taken per shipment, and nothing on this page is an offer.
