SES OPTKMUI Multi-Unit Interface for CAT / TEC Telephone Entry Systems
The OPTKMUI is the Select Engineered Systems multi-unit interface, often called the MUI. Its job is to let multiple compatible SES telephone entry units share a single telephone line in supported configurations. This can be useful at properties with more than one entry point where the existing design uses one line for several CAT or TEC panels.
This part should be ordered by the system design, not just by the product family name. SES references note that one MUI is required for each unit placed on the single shared line, and the maximum supported count is commonly listed as up to 8 units. Wiring layout, line quality, and programming can affect performance, so the entire installation should be reviewed before replacing or adding an MUI.
Compatible With
Commonly associated SES systems
- Select Engineered Systems CAT systems where OPTKMUI is specified
- Select Engineered Systems TEC / TEC II systems where OPTKMUI is specified
- Select CAT Card and CAT telephone entry/card access systems that support MUI line sharing
- Multi-entry properties where up to 8 supported SES units share one telephone line
Application notes
- One OPTKMUI is commonly required for each SES unit placed on the shared phone line
- Not a modem, network interface, relay board, or cellular interface
- Line sharing should be verified against the SES wiring documentation
Features and Specifications
| Manufacturer | Select Engineered Systems |
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| Product Type | Multi-unit telephone line interface |
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| Part Number | OPTKMUI |
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| Application | Allows supported CAT/TEC units to share a single telephone line |
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| Compatible Operator Type | Telephone entry / access-control systems |
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| System Capacity Notes | Commonly referenced for up to 8 CAT or TEC units on one line where supported |
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| Notes | One interface may be required per unit on the shared line |
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Also Known As / Related Part Numbers
- OPTKMUI
- SES-OPTKMUI
- MUI
- Multi Unit Interface
- Allows up to 8 CAT systems to share a single telephone line
- Allows up to 8 TEC systems to share a single telephone line
- 262487 - distributor catalog reference commonly associated with OPTKMUI
Technician Note
When troubleshooting shared-line telephone entry systems, test each unit and line segment separately. A wiring or line issue can look like a failed MUI.
Before Ordering Checklist
- Confirm the system uses compatible SES CAT or TEC units.
- Count the number of entry units sharing the phone line.
- Verify that one MUI is provided for each required unit where applicable.
- Check phone-line quality and wiring layout.
- Do not confuse OPTKMUI with modem, serial, network, or cellular options.
Professional Advisory
Phone-line sharing on access-control systems should be wired and tested by a technician familiar with SES telephone entry equipment.
Important Ordering Warnings
Do not exceed supported line-sharing configurations or parallel-wire panels without following SES documentation.
Product Questions and Answers
What does OPTKMUI do?
It allows supported SES CAT or TEC telephone entry units to share a single telephone line in approved multi-unit configurations.
How many units can share one line?
SES references commonly describe up to 8 supported CAT or TEC units, but the final layout should be checked against the system documentation.
Do I need one MUI for each entry unit?
SES references commonly state that one is required for each unit placed on the shared single line.
Is this a modem or network card?
No. It is a multi-unit telephone line interface, not a modem, IP network module, or cellular conversion kit.
Can this fix poor telephone audio?
Not necessarily. Poor audio can be caused by line quality, wiring, grounding, speaker/microphone issues, or the host unit.
