What Does a Sign Language Interpreter Do and How Do You Work With One?

A sign language interpreter converts meaning between a signed language and a spoken language in real time, in both directions, so a Deaf and a hearing person can hold an actual conversation. You need one whenever the exchange is live and interactive — a doctor's visit, a job interview, a parent-teacher meeting, a phone call. You do not need an interpreter for a written document (that's translation) or for one-way speech you only need to read (that's captioning). The rest of this article explains the difference, the main ways interpreting is delivered, what credentials to look for, and how to book and run a session without surprises.

Interpreter vs. translator vs. captioning: three different jobs

These terms get used interchangeably, but they solve different problems.

The key distinction is interactivity. An interpreter is a person in the loop who can ask for clarification, handle interruptions, and switch speakers mid-sentence. Captioning shows you what was said but doesn't speak back for you. That's why captioning apps and interpreters are complements, not substitutes — see the section on phone calls below.

The main ways interpreting is delivered

In-person interpreting

The interpreter is physically in the room. Best for situations with lots of visual context, multiple speakers, or where you need to read body language and room dynamics — medical exams, courtrooms, large meetings.

Video remote interpreting (VRI)

The interpreter appears on a screen (tablet, laptop, or dedicated unit) while the Deaf and hearing parties are together in one location. Useful when you need an interpreter now and can't wait for one to travel, or in rural areas. It depends heavily on a stable, high-bandwidth connection and good camera framing.

Video relay service (VRS)

A specific use of VRI for phone calls. The Deaf caller signs to the interpreter over video; the interpreter voices to the hearing party on the phone, and voices the reply back in sign. This is how many Deaf people make ordinary phone calls to businesses, banks, and government offices.

What credentials and quality signals to check

Certification and licensing rules vary by country and region, so verify what applies where you are. In the United States, the recognized professional credential is RID certification (from the Registry of Interpreters for the Deaf), and many states also require a state license or have their own screening. When you book, it's reasonable to ask:

• Which certification(s) the interpreter holds, and whether your state requires a license.
• Whether they have experience in your specific setting (medical, legal, educational, technical).
• Whether they've worked with the specialized vocabulary involved — for example, a cardiology consult or a software engineering interview.

For anything with legal or medical consequences, a certified interpreter isn't just preferable — it may be a legal requirement. Don't accept a well-meaning bilingual friend or family member as a substitute in those settings; it creates conflicts of interest and accuracy problems.

How to book an interpreter: the details that prevent problems

Give the agency or interpreter these facts up front. Missing any of them is the most common cause of a bad session.

• Setting and purpose — what kind of appointment or event, and what will be discussed.
• Date, start time, and expected duration — plus buffer if it might run long. Interpreting is cognitively intense; sessions typically need a second interpreter for long blocks, so tell them the real length.
• Number of Deaf participants — one Deaf person signing to a group is a different job than a group discussion with several signers.
• Number of hearing participants and how they'll speak — one speaker, a panel, or open discussion changes the setup.
• Specialized vocabulary or names — send an agenda, slide deck, or list of technical terms in advance. This is the single biggest quality lever you control.
• Format — in-person, VRI, or VRS — and the platform or equipment involved.
• Any accessibility needs on the Deaf side — preferred sign language or dialect, since signed languages are not universal (American Sign Language, British Sign Language, and others are distinct).

Running the session well

A few habits make interpreting work far better:

• Speak to the Deaf person, not the interpreter. The interpreter is a conduit, not a participant. Say "What do you think?" to the person, not "Ask her what she thinks."
• One person speaks at a time. Overlapping speech is the hardest thing to interpret.
• Pause for the interpretation. The interpreter needs a beat to finish before the next person starts.
• Don't ask the interpreter to editorialize or summarize. Their job is to convey meaning faithfully, including tone.
• Flag problems openly. If the video freezes, audio drops, or something was misheard, say so immediately rather than pushing through.

Where captioning and transcription apps fit

Interpreters handle live, two-way signed conversation. For phone calls and one-on-one spoken conversations, a captioning or live-transcription app can cover a lot of ground on its own — and it's often faster to start than booking an interpreter.

Rylo, for example, is a call captioning and live transcription app that shows every word as it's spoken during calls made through the app, keeps your existing phone number, supports 50+ languages with real-time language detection, and saves transcripts locally on your device. It's certified by the FCC and offered at no cost to individuals with hearing loss, and it works alongside hearing aids, cochlear implants, and Bluetooth headsets. For a Deaf signer who needs to sign on a call, a video relay service is still the right tool; for a hard-of-hearing person who speaks and needs to read the other side, captioning is the direct fit. Many people use both depending on the call.

Common problems and how to fix them

The interpreter doesn't show up. Confirm the booking 24–48 hours ahead, get a direct contact number, and have a backup — a VRI provider you can reach on short notice.

Role boundaries blur. If the interpreter starts answering for the Deaf person or offering opinions, redirect: "Please interpret what I said." This is a training issue, not a reason to abandon the session.

Poor video or audio. For VRI, test the connection and camera framing before the appointment, use a wired connection if possible, and position the camera so the interpreter can see hands and face clearly.

The wrong interpreter for the content. If specialized vocabulary is being fumbled, request a different interpreter or one with subject-matter experience for the next session.

Uncertainty about whether a certified interpreter is required. For legal, medical, and government settings, assume yes and confirm the specific rule with the provider or the institution. Getting this wrong can invalidate a proceeding or compromise care.

Quick decision guide

• Live conversation, signed, two-way → book an interpreter (in-person or VRI).
• Phone call where you sign → video relay service (VRS).
• Phone call or one-on-one where you speak and need to read → captioning/transcription app such as Rylo.
• Written document → translator.
• Legal, medical, or official setting → certified interpreter, verified credentials, booked with full details in advance.