3M 478DA (D-15) Installation Manual - page 3

WARNING: 

All intercom and vehicle detection cables must route through a CONDUIT THAT IS SEPARATE from 

that containing sign lighting. Do not, under any circumstances, route audio or low voltage cables in the 

same conduit with 120 VAC wiring. This violates the National Electrical Code and presents a potential 

hazard. 

2.     OUTSIDE SPEAKER/MIC - The D-15 intercom provides two-way communication to a remote 8-ohm speaker. A 

weatherproof horn-type speaker is acceptable for most drive-thru applications, although best audio clarity is achieved 

with the use of a separate speaker and microphone. The 3M OSM (78-8016-9810-7) can be used for most menu sign 

and point-to-point communications. The 3M Security Speaker/Mic (78-8028-9047-1) is recommended for pass-

through window applications. Place the speaker at a height of 42 to 54 inches above the driveway surface to reduce 

vehicle noise. Connect to the SPEAKER outputs as shown in figure 3. 

3.    SPLIT SPEAKER AND MICROPHONE - The D-15 allows the connection of separate components for 

incoming and outgoing audio. To select this option, set SW104 and SW105 to the OUTSIDE MIC position (see figure 

1). A low-impedance dynamic microphone may be connected to the OUTSIDE MIC inputs and the outgoing audio will 

still be on the SPEAKER outputs (see figure 3). 

4.     FLEX MICROPHONE - A low-impedance microphone may be substituted for the internal D-15 mic to place the 

microphone closer to the operator for better voice clarity in noisy situations. Set SW102 & SW103 to the EXTERNAL 

MIC position (see figure 1) and connect the microphone to the FLEX MIC and SHIELD inputs (see figure 3). 

5.     MONITOR SPEAKER - An 8-ohm speaker may be connected to the monitor outputs to monitor the incoming 

conversation. Use twisted pair wire to connect this monitor speaker to the MONITOR HI (or MONITOR LO) and 

COMMON outputs (see figure 3). MONITOR LO is the same power output as the internal speaker, MONITOR HI 

outputs a higher level. 

6.     FOOTSWITCH - The Talk/Listen function of the D-15 can be controlled by an external footswitch normally open 

contact. Connect the footswitch(s) to the FOOTSWITCH and COMMON inputs (see figure 4). The D-15 Talk/Listen 

switch remains functional. 

7.    MULTIPLE MASTER SYSTEM - The Model 478DA allows the connection of two units to the same outside 

speaker/microphone Connect the speaker outputs per figure 5. Route 2 twisted pair cables between the units and 

connect to the BUSY, ALERT CANCEL, VEHICLE DET. +20VDC and COMMON inputs of each unit 

8.    MUSIC/MESSAGE PLAYBACK SYSTEM - The 8-ohm output from the power amplifier of a music or 

message playback system may be routed through the D-15 to the outside speaker/mic. This signal will be muted 

during D-15 talk/listen functions and fed through when the unit is in standby. Connect the music/message source's 

amplified output to the "MUSIC IN" inputs per figure 4. NOTE: THIS OPTION CANNOT BE USED WITH SYSTEMS 

IN THE MULTIPLE MASTER CONFIGURATION. 

9.    HEAVY-DUTY HANDSET (OUTSIDE) - Connect as shown in Figure 4. 

10.   VEHICLE DETECTION - Install the vehicle detection system per individual instructions. Set the Magnetic Loop 

Detector to "Presence" mode.