# OpenScape 4000 STMD3a — ISDN S0 Station/Trunk Module (Variant A)

URL: https://www.promark.tr/en/products/stmd3a
Category: Expansion Cards & Modules
Family: [OpenScape 4000 Cards](https://www.promark.tr/en/products/openscape-4000-cards)

Variant A of the STMD3 board, combining STMD and SLMS functions on one card. 8 S0 trunk interfaces (each 2B+D); function-equivalent to STMD2 with new hardware. SIPAC backplane connector, on-board flash protection.

## Key features

- 8 S0 trunk interfaces (4-wire) — each provides 2B (64 kbit each, voice/data) + D (16 kbit) basic access.
- Combines STMD (trunk) and SLMS (station) on one board — STMD2 + SLMS2 unified.
- Function-equivalent to STMD2 with a new source number and new components.
- SIPAC connector — refreshed backplane interface.
- Front panel: 2 status LEDs.
- On-board flash protection — see §2.3 lightning protection.
- Short-bus mode (1–8 TE distribution): cable limit ~60 m.
- Extended bus mode via AMO SBCSU EXTBUS=YES → up to 160 m cable.
- MDF cabling differs from STMD2's 24-twisted-wire unprotected approach (new cable standard).

## Specifications

- **Type:** Station/Trunk Module Digital S0
- **Variant:** A
- **Trunk interfaces:** 8 × S0 (4-wire)
- **S0 access type:** Basic Rate (2B + D)
- **Bandwidth per channel:** 64 kbit (B) + 16 kbit (D)
- **Replaces:** STMD2 + SLMS2 (functionally equivalent)
- **Connector:** SIPAC
- **LEDs:** 2 (front panel)
- **Flash protection:** On-board
- **Short bus cable limit:** ≈ 60 m
- **Extended bus:** Max. 160 m (AMO SBCSU EXTBUS=YES)
- **MDF cable:** New standard (differs from STMD2)

## Use cases

- Preserve existing ISDN S0 plant — STMD2 → STMD3a refresh.
- European ISDN BRI external trunk — combined trunk + station roles.
- Hotel internal ISDN S0 phones — for executive digital terminals.
- Long building campus — extended bus (160 m) for runs that need longer cabling.
- Lightning-prone regions — on-board flash protection for external trunks.

## For a quote and BOM

https://www.promark.tr/en/contact · +90 312 544 0915 · destek@promark.tr