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
| Display / symptom | Meaning | First checks |
|---|---|---|
| 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 |
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
| 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 |
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 | Meaning | Suggested Fix |
|---|---|---|
| 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 |