By TEBAOFLEX Jyen. Originally published on June 22, 2026.
What TP adds
A conventional LiYCY cable has multiple conductors within an overall copper braid screen. A LiYCY-TP construction arranges conductors as twisted pairs. The exact pairing, conductor dimensions, screen coverage and electrical data still come from the chosen product specification.
Twisting helps a balanced circuit expose both conductors to similar interference and can reduce differential pickup. Pair geometry can also influence coupling between adjacent circuits. It is not proof of a fixed crosstalk improvement at every frequency.
An overall screen is not an individual pair screen
The common braid helps control coupling between the cable and its surroundings when terminated appropriately. It does not physically separate every internal circuit from its neighbors. Where the signal design requires individually screened pairs, an overall-screen-only cable is not an equivalent substitute.
Do not assume that LiYCY-TP has controlled 120-ohm impedance merely because its cores are twisted. For RS-485 or another data interface, select a cable with the required impedance, attenuation, resistance and installation rating.
RS-485 length depends on the whole link
RS-485 wiring is a distributed transmission line. Data rate, driver edge rate, cable loss, termination, stubs, node loading and common-mode conditions affect operation. A one-pole RC time constant cannot establish the maximum range of an installed network.
Use the equipment wiring rules and a suitable bus topology. Fit termination where required by the link design, normally at the ends of the main line rather than indiscriminately at every device. Validate the receiver signal and communication performance at the actual operating rate.
Generic claims of 1,200 m at a stated baud rate are not guarantees for arbitrary LiYCY cable, connectors and node counts. Retain margin for temperature, tolerance and electromagnetic disturbance.
A separate DC-loop calculation
For a hypothetical instrument loop, assume 4.5 V is available for cable drop at 22 mA. The permitted loop resistance is 4.5/0.022 = 204.55 ohms. If the outgoing-and-return resistance is 78 ohms per kilometre of route, the voltage-drop-only length is about 2.62 km.
This calculation does not approve that length for HART or any other communications overlay. Device burden, barrier requirements, capacitance, inductance, frequency response and the actual alarm/startup current need separate checks. The assumed 4.5 V allowance is not a universal standard requirement.
Pairing, identification and acceptance
Keep each signal and its intended return in the assigned pair and preserve the twist close to the termination. Verify the supplier color code; two separate solid green and yellow cores are not the same as a green/yellow bicolored protective conductor. Never repurpose a designated protective conductor as an ordinary signal wire.
Confirm continuity, pair mapping, shielding and insulation using the equipment-safe test procedure. Where crosstalk is specified, record its frequency, fixture, source/load conditions and acceptance limits. No proprietary NEXT data or measured transmission distance is asserted here.
Primary references and specification evidence
The references explain the cited technology or manufacturer example. They are not TEBAOFLEX product approvals or evidence that a supplied batch has passed the tests. Request the exact product drawing, specification edition, acceptance criteria and traceable records.
Discuss your application
Discuss the duty, installation and required documentary evidence with TEBAOFLEX. WhatsApp: +86 185 9591 3361. Product suitability and test obligations must be confirmed for the specific order.