Sound system & audio (meetinghouses)

(Redirected from Crab box)

All content on this page is moving to LDS Help Center under the Meetinghouse Technology topic. This page was supposed to be deleted at the end of October 2012.


Stake technology specialists are responsible for all electronic devices in meetinghouses.

Sound system




Note: While buildings vary in how the sound system is implemented, the instructions should cover the typical case.


Multiple input adapter box (aka audio interconnect box or "crab box")

The multiple input adapter box has a variety of cables and connections allowing one to connect most any electronic audio source (VCR, DVD, CD, MP3 player, laptop computer, mixer, etc) to the XLR mic-level input of the typical chapel or cultural hall. Due to its many cables, the box is sometimes referred to as the "Crab Box." Typically a Crab Box is either a model EJ-10 (gray case) or EJ-8 (black case).

The Crab Box requires a source with higher level output such as Line, Speaker or Headphone. It cannot work with mic-level sources.

The EJ-10 has the ability to connect to the phone line - either to feed telephone audio to a remote site or to receive audio. Some examples of this use is to use as a backup to hear priesthood session of General Conference if the satellite broadcast should fail, or use a pair of them as backup to the Meetinghouse Webcast system. Note, the EJ-8 does not have the telephone features

In older systems which do not have a line level input into the system, the EJ-8, and EJ-10 allow the connection of any non-mic-level signal into the building sound system. Since the EJ-8/10 have a volume control, various input devices can be adjusted for appropriate levels, such as a DVD player with "soft" audio.

The Church issues at least one audio interconnect box to a building. The box is usually stored in the library.

EJ-8 Information

EJ-10 Information

Wireless microphones

The Presiding Bishopric has approved the use of wireless microphones in LDS stake centers. The Facility Manager may have additional ones to use when needed. There is a choice of microphones - lapel mic or hand held. More than one microphone can not be used with the same receiver. If more wireless units are needed, one receiver and microphone will be needed for each set.

Wireless microphones are co-ordinated through the Stake PFR and then through the facility manager. The wireless microphones distributed by the Church (Audio Technica) are the only ones officially supported.

Interpretation equipment

Congregations with multiple language needs should co-ordinate with their FM Group. The FM Group will obtain the equipment necessary to provide simultaneous interpretation of the meeting. Members and investigators needing translation assistance use special receivers and headphones. Interpretation systems are portable and can, therefore, be taken to stake conferences and leadership meetings and also used at firesides and other meetings away from the chapel.

An interpreter speaks into a microphone and transmitter which broadcasts his words to people in the congregation. A loud voice is not necessary as the interpreter’s microphone is sensitive enough for even a whisper. In years past, Steno-masks were used, but they have been supplanted by the current head-worn headset/microphone for hygiene and cost reasons.

Williams Sound manufactures the systems, and the church has specific equipment models that are approved for use. When equipment is required, current models will be supplied. Older equipment models have proved very durable and are still in use today; all new equipment is compatible with older equipment.

Use for broadcasts

An unbalanced line-level input is available on the transmitter’s back panel. This is a phono (RCA) jack. You may use a short jumper cable connecting the transmitter to the audio output from a VCR or television monitor connected to the building’s satellite system and tuned to the language you need. This facilitates integration of the whole congregation rather than dividing them by language into separate rooms. Your FM Group can assist you in these connections.


This page was last modified on 5 April 2016, at 09:39.

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