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Which Hochiki CHQ output module should I use — DRC2, MRC2, DSC2 or PCM?

Match the load to the module: DRC2 for two low-voltage relays, MRC2 for mains switching, DSC2 for monitored sounder lines, PCM for four inputs plus four relays.

Direct answer

Hochiki CHQ output modules cover different load types on the ESP loop: CHQ-DRC2(SCI) provides two independently driven volt-free changeover relay outputs (30 V DC max, 1 A resistive); CHQ-MRC2(SCI) provides a single mains relay (250 V AC max, 5 A resistive, or 48 V DC max, 2 A resistive) with no internal fuse; CHQ-DSC2(SCI) provides two monitored sounder outputs (1 A per line) rather than relay contacts; and CHQ-PCM(SCI) provides four monitored inputs plus four changeover relay outputs. All four modules are also available in a DIN-rail enclosure. The superseded codes CHQ-DRC, CHQ-MRC and CHQ-DSC follow the same guidance.

Applies to

  • Products / Models: CHQ-DRC2(SCI), CHQ-MRC2(SCI), CHQ-DSC2(SCI), CHQ-PCM(SCI), and the corresponding /DIN(SCI) variants. The superseded codes CHQ-DRC, CHQ-MRC and CHQ-DSC are covered by the same guidance.
  • Firmware / Version: Not applicable
  • Region: Not applicable
  • Standards: BS EN 54-17 (short-circuit isolators) and BS EN 54-18 (input/output devices)

Summary

This article covers the physical sizing, relay/output ratings, channel counts and monitored-input behaviour for the CHQ-DRC2(SCI), CHQ-MRC2(SCI), CHQ-DSC2(SCI) and CHQ-PCM(SCI) output modules.

Key specifications and characteristics

  • CHQ-DRC2(SCI)

    • Function: Two independent, separately driven volt-free changeover relay outputs (dual relay controller).
    • Dimensions: “Smart-Fix” module 157 × 127 × 35 mm (module plus lid; 79 mm deep with the CHQ-BACKBOX). DIN-rail enclosure (CHQ-DRC2/DIN(SCI)) 119 × 108 × 24 mm.
    • Relay rating: Two independent N/O and N/C volt-free changeover outputs, rated 30 V DC max, 1 A (resistive load), driven separately.
    • Use case: Provides two outputs when a dual-output module is required (alternative to using two single-output modules), for example controlling dampers or plant and equipment shutdown.

  • CHQ-MRC2(SCI) — Mains Relay Controller

    • Function: A single mains-rated changeover relay output, with the N/O, N/C and COMMON contacts brought out to screw terminals.
    • Dimensions: “Smart-Fix” module 157 × 127 × 35 mm. DIN-rail enclosure (CHQ-MRC2/DIN(SCI)) 119 × 108 × 24 mm.
    • Relay rating: Rated 250 V AC max, 5 A (resistive), or 48 V DC max, 2 A (resistive). No fuse is fitted in the module, so the relay output circuit should be protected by a suitable over-current protective device, and for mains AC switching the control panel must comply with the Low Voltage Directive for SELV circuits.
    • Recommended application: Suited to mains-related equipment (for example, to switch a gas solenoid or other mains loads).

  • CHQ-DSC2(SCI)

    • Function: Dual Sounder Controller — two independently driven sounder outputs, each fully monitored for open and short circuit (monitoring can be disabled per output).
    • Output rating: 1 A per line maximum (each line fused at 1.25 A), from a separate 20–28.8 V DC (24 V DC nominal) auxiliary supply; sounder end-of-line resistor 1 kΩ ±5%, 2 W.
    • Use case: Driving conventional sounders from the loop under panel synchronisation. It is not a relay module and should not be used for door release or other dry-contact switching.

  • CHQ-PCM(SCI) (Plant Control Module)

    • Inputs and outputs:
      • Four monitored inputs, each configurable to monitor either a normally open or a normally closed volt-free contact.
      • Four independent changeover relay outputs with N/O and N/C volt-free contacts, rated 30 V DC max, 1 A (resistive).
    • Form factor variants:
      • The DIN-rail variant is CHQ-PCM/DIN(SCI); mount it in a suitable enclosure on a standard 35 mm “top hat” DIN rail (NS 35 mounting rail), with the loop connections at the bottom of the unit; Hochiki recommends the SMB-2 and SMB-3 boxes for this purpose.

Inputs and panel configuration

  • The CHQ-DRC2(SCI), CHQ-MRC2(SCI) and CHQ-DSC2(SCI) each provide one auxiliary monitored input for local fire and fault monitoring; the CHQ-PCM(SCI) provides four. All are fully supervised for open and short circuit, and supervision can be disabled by DIL switch (in pairs on the PCM).
  • Each CHQ-PCM(SCI) input can be set to monitor either a normally open or a normally closed volt-free contact.
  • How an input is mapped to a cause-and-effect action is a control panel function; confirm it in the manual for the specific panel.

Selection guidance (based on relay ratings and function)

  • Use CHQ-DRC2(SCI) for low-voltage DC switching such as magnetic door releases (relay contacts rated 30 V DC max, 1 A resistive).
  • Use CHQ-MRC2(SCI) modules for mains switching requirements (250 V AC max, 5 A resistive, or 48 V DC max, 2 A resistive).
  • Use CHQ-DRC2(SCI) when two separate relay outputs are required in one module.
  • Use CHQ-PCM(SCI) when multiple monitored inputs and multiple relay outputs are needed (four inputs + four relays) in a single loop address.

Practical notes

  • If only a single output is required, the CHQ-SOM single output module provides one volt-free contact, configurable N/O or N/C and rated 30 V DC max, 1 A (resistive); where two outputs are required, the CHQ-DRC2(SCI) provides a dual-output solution. The CHQ-SOM is a bare module with flying leads. To maintain its LPCB approval, it must be mounted with the SMB-ADAPTOR plate in an SMB-1 enclosure or in an equivalent enclosure made from polycarbonate or a similar impact-resistant material (EN 54-18:2005, clause 5.9).
  • When planning multiple door outputs, choosing CHQ-DRC2(SCI) modules (two relay outputs per module, 30 V DC max, 1 A resistive) may be more cost- and space-effective than fitting multiple single-output CHQ-SOM modules.
  • The CHQ-PCM(SCI) supports individual use of each input and relay channel and is suitable for interfacing multiple signals and control outputs in plant or containerised installations.
  • For conventional zone inputs on the same loop, see Which Hochiki CHQ zone monitor do I need - CHQ-SZM2(SCI) or CHQ-DZM(SCI)?. For replacing an 8-input/8-output interface unit with CHQ-PCM(SCI) modules, see What replaces the MIOU or CHQ-FIO when I need eight inputs and eight outputs?

When to contact technical support

  • You need to confirm the over-current protection arrangement for CHQ-MRC2(SCI) mains AC switching on your installation.
  • You are unsure whether to specify the “Smart-Fix” or DIN-rail enclosure variant for the available panel space.

Safety note

This article is general guidance for Hochiki Europe products. Design, installation, commissioning, maintenance and modification of fire detection and alarm systems should be carried out by, or under the responsibility of, a competent person in accordance with the applicable standards (for example BS 5839-1 in the UK). Statutory requirements imposed by the relevant enforcing authority also apply. Always refer to the current product manual and data sheet for the exact model before carrying out any work.

References

Last reviewed: 2026-10-13 — Reviewed by: Hochiki Europe Technical Support