Local Exchange Terminal POTS (L-POTS)
The LET Plain Old Telephone Service (L-POTS) plug-in card provides six loop start POTS circuits. The L-POTS card delivers Loop-Start-Only signaling with ring cadence following, on-hook transmission between ring bursts, and forward disconnect. The L-POTS card also provides a high on-hook DC resistance and a universal ringing detector. In addition, L-POTS card supports Call Message Waiting Indicator (CMWI) and is MLT (Mechanized Loop Testing) capable. Install the L-POTS plug-in card in the LET; install its counterpart, the RST POTS plug-in card (R-POTS), in the RST.

Features and Benefits

  • On-hook transmission (CLASS) capability
  • Forward disconnect
  • 900 Ω local exchange impedance
  • Compatible with the following test systems MLT, Teradyne 4TEL and Reltec
  • Call Message Waiting Indicator (CMWI)

Included Highlights

Voice Service

Install the L-POTS card in the LET to provide universal (TR-57) POTS service and install its counterpart, the R-POTS card, in the Remote Subscriber Terminal (RST).


You can insert the L-POTS card into any general purpose slot at a LET, allowing up to 100% slot population in a single shelf.

Testing Capabilities

Compatible with the following test systems, including MLT, Teradyne 4TEL and Reltec.


  • Supported in Tellabs 1000 CBA
Software Support
  • Minimum base software FP16 and higher
  • Craft User Interface (CUI)
  • Tellabs Panorama Element Management System (EMS)
LED Indicators
  • FAIL (red)
  • BUSY (green)
  • DLC Test Resources In Use Signatures: Tip-to-Ground, Ring-to-Ground 169 kΩ and Tip-to Ring 300 kΩ
  • Reltec DC Signatures Off-Hook: Tip-to-Ground and Ring-to-Ground 445 kΩ and Tip-to-Ring >1200 MΩ
  • Reltec DC Signatures On-Hook: Tip-to Ground and Ring-to-Ground 445 kΩ and Tip-to-Ring > 2 MΩ
  • MLT/Teradyne DC Signatures Off-Hook: Tip-to-Ground, Ring-to-Ground 430 kΩ and Tip-to-Ring 900Ω
  • MLT/Teradyne DC Signatures On-Hook: Tip-to-Ground and Ring-to-Ground 430 kΩ and Tip-to-Ring > 2 MΩ
  • 2-wire return loss: ERL 18 dB - SRL > 10 dB
  • Maximum VF overload level: +5 dBm
  • Nominal net loss (referenced 2-wire 900Ω): 0 dBm ± 0.4 dB
  • Nominal VF input impedance: 900 Ω + 2.16 μF
  • Audio Companding: μ-Law
  • Maximum CO wiring resistance: 200 Ω
  • Normal open interval detector threshold: 10 mA ± 3 mA
  • Nominal DC input resistance: 930 Ω
  • Ring detector sensitivity: 50 Vrms (17 to 33 Hz)
  • AC ringing load (20 Hz): 7 kΩ ± 10 %
  • Ring detection: < 150 ms
  • Pulse distortion (pw > 50 msec): < 10 ms
  • End to end signaling delay (normal): < 50 ms
  • TR-TSY-000057
  • Altitude: Up to 10,000 feet
  • Relative Humidity: 5–95% noncondensing
  • Temperature: -40° to +149° F (-40° to +65° C)
Alarm / Monitor / Test
  • MLT
  • Teradyne 4TEL
  • Reltec
Power Consumption
  • Typical power consumption: 0.62 W
  • Maximum power consumption:
  • Six (6) 2-wire circuits
  • Weight: 0.5 lb (0.23 kg)
  • Depth: 10.5 in (26.67 cm)
  • Width: 0.563 in (1.429 cm)
  • Height: 5.125 in (13.018 cm)
Product Specifications Sheet

Local Exchange Terminal POTS (L-POTS)
Product Specifications
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