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


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.

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).

Testing Capabilities

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


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

Local Exchange Terminal POTS (L-POTS)
Product Specifications
Related Services
Technical Support

Ongoing network support services to ensure peak performance during the operation and maintenance of your network.

Professional Services

The right professional network services to help you successfully plan, design, install, and operate your network.

Digital Credentials

Digital versions of your Tellabs-earned training credentials that can be used in email signatures, digital resumes, and on social media sites.


Flexible network training options to educate your staff on how to expertly plan, implement, and support your network.

Email Us
To place an order or reach customer service, email directly at
Technical Support
Call Us
Call us for immediate customer service and assistance.
Corporate Headquarters
Technical Assistance Center (TAC)