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 MAXSYS Programmable-Message LCD Keypad (ID 6)
- LCD4501(T) Installation Manual; MAXSYS PC4020 Install Manual keypad section — DSC official documentation
Error Codes
Keypad and panel troubles display on this device using **[*, 2] (where supported) or dedicated trouble LEDs. Use the host panel install manual** for full trouble lists — below covers common keypad-specific symptoms.
Common keypad / operator faults
LCD4500 / LCD4501 keypad troubles
- **
[*, 2]scrolls MAXSYS troubles;[#]** silences trouble beep. - Service Required sub-codes map to Appendix D in PC4020 install manual.
- Blank LCD with panel powered usually means Combus address not enrolled or wiring open.
LCD4500 / LCD4501 MAXSYS keypad
Keypad addresses 9–24 on PC4020 diagnostics map.
Panel trouble reference
Keypads display panel-level troubles (AC loss, FTC, zone faults) — fix the underlying circuit or device, not the keypad, when [*, 2] points to panel/comms/zone issues.
Source: LCD4501(T) Installation Manual; MAXSYS PC4020 Install Manual keypad section; host panel user/install manual trouble sections.
| Code / display | Meaning | What to do |
|---|---|---|
| Blank / dead display | No power or bus communication | AC, battery, bus wiring, keypad address, fuse |
| Keypad Tamper | Enclosure opened or tamper switch | Mounting plate, tamper jumper, cover fit |
| Cannot Arm / Not Ready | Open zones or active troubles | `[*, 2]` trouble scroll; close zones; clear troubles |
| Invalid Code / Access Denied | Wrong user code or authority level | User `[5]` programming; verify partition assignment |
| Combus Communication Fault | MAXSYS lost keypad module | Combus wiring, termination, module address |
| Cannot Enter Programming | Keypad lacks installer authority | Installer code `[*, 8]`; partition/global assignment |
| Command / display | Action | |
| `[*, 2]` + scroll | View troubles — panel beeps every 10 s until cleared | |
| `[#]` | Silence trouble beep | |
| Module diagnostics `[04]` | E = Combus comms, T = tamper, LV = low voltage |
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 the Compatible Peripherals section.
- 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.
Compatible Peripherals
This page lists which alarm panels this keypad works with — not sensors, modules, or communicators.
Host panels
| Host panel | Connection |
|---|---|
| MAXSYS PC4010 / PC4020 | Combus keypad — assign address in DLS or keypad enrollment |
Related notes
- Graphic annunciators PC4632/PC4664 (separate Combus devices)
- MAXSYS Combus modules and communicators per install manual
Not compatible
- PowerSeries Keybus panels (PK5500 family)
- PowerSeries Neo Corbus HS2 keypads
- IMPASSA WT5500 wireless keypads
Replacement warning
Keypads are not universal across DSC generations. Confirm bus type, address programming section, and firmware before substituting another model.
Source: LCD4501(T) Installation Manual; MAXSYS PC4020 Install Manual keypad section (DSC official documentation).
Installation Notes
Follow LCD4501(T) Installation Manual; MAXSYS PC4020 Install Manual keypad section for mounting, wiring, addressing, and enrollment. Summary below — not a substitute for the full manual.
Pre-install checklist
- Match keypad SKU to host panel family (see the Compatible Peripherals section).
- Select mounting height and tamper-secure back box per local code.
- Reserve bus power or confirm wireless transceiver capacity on panel.
- Plan partition and global keypad roles for multi-partition installs.
Typical install sequence
- Mount keypad back box and pull bus or confirm wireless coverage at location.
- Wire Keybus/Corbus homerun or begin wireless enrollment per manual.
- Assign keypad address in panel programming (
[013]PowerSeries,[902]Neo/Pro, DLS for MAXSYS). - Set partition assignment and display options.
- Test arming, disarming, trouble display, and prox/RF features if equipped.
- Document address, partition, and installer access for service handoff.
Regional notes
T suffix models for telco/listed variants — match manual to label
Source: LCD4501(T) Installation Manual; MAXSYS PC4020 Install Manual keypad section (DSC official documentation).