Overview
LCD4500/LCD4501/LCD5500Z programmable-message keypads are operator interfaces for MAXSYS PC4010/PC4020 systems. They support full status, arming, programming entry, and trouble scroll on Combus.
Panel bus / link type
Combus (MAXSYS)
At a Glance
| Detail | Value |
|---|---|
| Product type | Alarm keypad / operator interface |
| Model family (LCD4500, LCD4501, LCD4501T, LCD5500Z) | See label and install manual |
| Bus / wireless link | Combus (MAXSYS) |
| Primary manual | LCD4501(T) Installation Manual; MAXSYS PC4020 Install Manual keypad section |
| Region / listing notes | T suffix models for telco/listed variants — match manual to label |
Before You Install or Replace One
- Confirm exact model number on the keypad label matches the install manual.
- Verify host panel family — Keybus PowerSeries, Neo Corbus, MAXSYS Combus, and IMPASSA wireless are not interchangeable.
- Plan unique keypad address or wireless enrollment — duplicates cause bus collisions or offline devices.
- Check partition assignment (global vs partition keypad) for multi-partition sites.
- Include keypad current draw in panel AUX / Corbus / battery standby calculations.
Official Sources
- Product page: DSC LCD5500Z (ID 965)
- LCD4501(T) Installation Manual; MAXSYS PC4020 Install Manual keypad section — DSC official documentation
Troubleshooting
Start with host panel family, then keypad model, then bus vs wireless link.
Quick diagnostic flow
- Confirm keypad model matches LCD4501(T) Installation Manual; MAXSYS PC4020 Install Manual keypad section.
- Verify host panel is on the supported list in compatible-peripherals.md.
- Check power: panel AC/battery healthy before blaming keypad.
- Read troubles at keypad with **
[*, 2]** or trouble LED. - Verify address / enrollment — wired:
[013]Keybus or[902]Corbus; wireless: enroll window and transceiver online. - Test with known-good user code on assigned partition.
Wiring / bus
- Keybus: homerun, polarity, termination; one bad keypad can drag bus if shorted.
- Corbus/Combus: homerun from panel module; check AUX/Corbus voltage under load.
- Wireless: battery, range, antenna, transceiver supervision on panel first.
MAXSYS LCD keypad service
- Confirm keypad address 9–24 range matches DLS programming.
- If only one LCD is dead, swap address with working keypad to isolate device vs bus.
- Programming entry: **
[*, 8, installer code]** at enrolled LCD.
MAXSYS LCD service
- Swap Corbus address with working LCD to isolate keypad vs bus leg.
- Programming entry: **
[*, 8, installer code]** at enrolled LCD.
After keypad replacement
Re-assign address, partition visibility, and user PINs per manual — new keypad does not inherit old device programming automatically.
Source: LCD4501(T) Installation Manual; MAXSYS PC4020 Install Manual keypad section; host panel installation guide keypad sections.