What Is Communicating Function, and Why Does It Exist?
This article explains communicating function locksets -- what they do, where they belong, and how they differ from the lockset functions specifiers more commonly encounter. It is aimed at commercial subs building hardware schedules, facility managers rekeying existing openings, and architects writing division 08 specs for multi-tenant or adjoining-room situations.
Communicating function -- commonly listed as F15 in ANSI/BHMA lock function tables -- means that both sides of the door require a key to operate the lever or knob. There is no inside button, no thumbturn, and no freely operating lever on either face. If you are standing on either side of that door without a key, you are not getting through.
That single trait separates communicating function from almost every other lockset function in a typical hardware schedule.
How F15 Differs from Functions You Already Know
It helps to compare communicating function against the most common alternatives:
- Passage (F01): No locking at all -- latch retracts freely from both sides. Used on interior corridors where access control is not needed.
- Office (F05): Outside locked by key; inside lever always free. The standard interior security function.
- Storeroom (F07/F08): Outside always locked; inside always free. High security, but only the outside is controlled.
- Communicating (F15): Key required on both sides. Neither side is ever freely operable without a credential.
That two-cylinder arrangement is the defining characteristic. In a mortise lockset, both escutcheons carry a cylinder. In a cylindrical (bored) lockset, the inside rose houses a cylinder instead of a thumbturn or button.
Where Communicating Function Actually Gets Specified
The name reflects the original use case: a door between two adjoining hotel or office suites that can be opened or locked from either tenant's side independently. But the application list runs wider than that.
Multi-Tenant Office and Co-Working Space
When two adjacent suites share a connecting door, neither tenant should have uncontrolled access to the other's space. Communicating function lets each tenant hold a key to their side. The property manager may hold a master that operates both cylinders, simplifying rekeying when tenants turn over.
Healthcare Suite Connections
Exam rooms, consultation rooms, and procedure suites that adjoin staff-only corridors benefit from two-cylinder control. The clinical team can pass through; a patient cannot exit into a restricted area without assistance. Life safety egress requirements must still be evaluated -- consult your authority having jurisdiction before specifying communicating function on any path of egress.
Retail Back-of-House and Stockroom Connections
A door between a retail showroom and a shared receiving corridor controlled by a building landlord is a natural fit. Neither party gets through without a key; each party holds only the cylinder relevant to their side.
School and Campus Buildings
Adjoining classroom suites, shared maker spaces, or departmental work areas that need to be independently secured after hours often appear in renovation projects. Communicating function avoids running additional wiring or card readers to what is essentially an interior-to-interior connection.
Keying Strategy: The Part Most Hardware Schedules Get Wrong
Because each side carries its own cylinder, the keying plan must address both independently. Common approaches:
- Same key, both sides: Convenient if one person or one organization controls the entire opening. Both cylinders are keyed alike or to the same master level.
- Different keys, different sides: Each tenant or occupant holds a key to their own cylinder only. The building master key operates both. This is the most common multi-tenant approach.
- Master-keyed systems: Communicating function cylinders can be incorporated into a large master key system just like any other mortise or cylindrical cylinder. Confirm cylinder format -- mortise vs. rim vs. bored -- before submitting the keying schedule.
Failing to think through the keying plan at the hardware-schedule stage is the most common mistake on these openings. Address it before the locksmith is on-site.
Mortise vs. Cylindrical: Which Body Type Fits?
Communicating function is available in both mortise and cylindrical (bored) lockset formats, though mortise is far more common in commercial applications because the larger case accommodates two full cylinder pockets cleanly.
- Mortise locksets in communicating function are well-suited to steel doors in office, healthcare, and institutional settings. Look for ANSI A156.13 Grade 1 rated bodies.
- Cylindrical locksets in communicating function (such as the Sargent 10 Line 10G30 communicating function) are an option for lighter-duty or retrofit situations where the door is already prepped for a bored lock.
Preferred manufacturers at DoorwaysPlus for these applications include Sargent, Corbin Russwin, and PDQ -- lines known for stable part availability and clear function-code documentation that holds up across a hardware schedule's lifecycle.
Fire-Rated Openings: Proceed Carefully
If the adjoining-room door carries a fire rating, communicating function introduces a complication: NFPA 80 requires that fire-rated door assemblies allow free egress from the side the occupant is on. A cylinder-only interior that prevents egress without a key may conflict with that requirement. Always confirm with your authority having jurisdiction and verify that any communicating function hardware on a rated assembly is specifically listed for that assembly. Do not rely on a cross-reference number alone to establish fire-label compliance.
Specifying It on the Hardware Schedule
When writing the hardware set, note the following:
- Call out F15 (communicating) explicitly -- do not let it default to office or storeroom function at the distributor.
- Specify cylinder format on both sides: mortise cylinder size, keyway, and finish must match the building master key system.
- Note keying requirements for both cylinders separately in the keying schedule narrative.
- If the door is in a hotel or multi-family project, coordinate with the guestroom hardware set -- hotel connecting doors have additional requirements covered separately.
DoorwaysPlus stocks communicating function locksets and can help you match the correct body, cylinder, and trim to your opening. If you are building a hardware schedule or need a compatible cylinder for an existing door, reach out to the team at DoorwaysPlus.com for expert guidance and competitive pricing.