Description:
The circuit shown is ideal in applications where paging levels are normally sufficient, but at times high ambient noise levels make the paging impossible to hear. This is common in factories where heavy machinery is in use at some times, making higher sound system levels necessary while the machinery is operating, then restoring the normal level when the machinery is no longer running.

In this example, the STP‑1 Universal Audio Attenuator is used to set two audio levels (normal and high) for the line‑level audio feeding the power amplifier for the machinery room. A sensing microphone is oriented to pick up machinery noise but not paging audio. Machine noise triggers the ST‑ACR1M which switches the higher audio input level to the amplifier. In the absence of machine noise, the ST‑ACR1M switches back to the standard paging level. An RDL TX‑70A Speaker Level Interface can be added to obtain line‑level paging audio from a constant voltage speaker line.

An RDL FP‑PA20A Power Amplifier is used in this example.

Description:
Speeches, government meetings, product announcements and other media events are occasions where a number of reporters in the electronic press require a high quality audio feed from the event organizers. The recording equipment in use might require a mic, balanced line level or unbalanced line‑level signal. It is critical that each feed is isolated so that if one feed is accidentally shorted or back‑fed, no other feed will be affected nor will the public address system. This example uses RDL STICK‑ONs® to provide isolated audio output signals driving a variety of audio jacks on a "Media Panel." An RDL RU‑MX4 Pro 4‑Input Mixer is used as the audio source. The line‑level source is distributed through an ST‑DA3 Audio Distribution Amplifier to line‑level outputs on RCA, 1/4¨ phone, and XLR jacks. The same source is padded down to mic level using an STP‑1 Attenuator and distributed through an STM‑DA3 Microphone Distribution Amplifier to the mic outputs. All jacks shown are on Decora® wall plates. These jacks are available in the RDL AMS series should a rack or tabletop mount be preferred. Distribution of video at these events can also be added using RDL composite and VGA/XGA distribution amplifiers.

Description:
This intercom application reduces the hardware requirements for a secure or weatherproof call box like those found in drive‑through talkback systems or secured entryways. The ST‑IC1 Intercom Amplifier input accepts a dynamic mic or phantom powered condenser mic. It can also use an 8 Ω or a 45 Ω speaker as a microphone element. An ST‑LCR1 Logic Controlled Relay is used in this application to switch a remote speaker so that it can function alternately as a speaker and as a microphone.

Description:
The mixing of multiple phantom‑powered mics is often required in various stage or public meeting room installations. The STD‑150 mixes the mic signals equally and passes phantom voltage generated by the mic preamp back to each of the mics. Each mic should have the same gain and should operate from a wide range of phantom voltage, as there is a small phantom voltage loss through the STD‑150. The STM‑3 works well in most applications but for critical, low noise installations the FP‑MP1 is recommended. The gain of the three microphones is set on the STM‑3. If individual mic gain adjustment is desired, use the RDL FP‑MX4 (4 channel ultra‑low‑noise mixer with switchable phantom and gain for each mic).

Description:
This application shows the layout of a two zone noise masking system. The white noise line output from the RDL ST‑NG1 feeds the inputs of two RDL FP‑PEQ3 parametric equalizers. The FP‑PEQ3 equalizers allow the installer to flatten the noise spectrum in each zone. The line output of each FP‑PEQ3 is fed through RDL FP‑PA20A 20W, 70/100 V power amplifiers. The 70 V output of each FP‑PA20A feeds multiple 70 V speakers in its associated zone. Multiple equalizers and amplifiers may be added for larger systems with more zones.

Description:
This application provides multiple paging locations, with priority assigned to each location. Each location has a mic with a PTT (push‑to‑talk) momentary pushbutton that provides external switching contacts. The STM‑2 preamp for each microphone should be installed near the associated mic. Wiring between each STM‑2 output and the corresponding ST‑VP1 is balanced, connected with shielded or unshielded twisted‑pair cable. When a PTT button associated with a microphone is depressed, the music fades down and paging becomes active. The highest priority mic overrides the lower priority mic(s). This arrangement may be carried out for an unlimited number of paging locations.

The FP‑PA20A 20 Watt Power Amplifier feeding 70 Volt speakers is used in this example. RDL offers a wide range of power amplifiers for paging and public address applications.

Description:
The RU‑VCA2 Local/Remote Controlled Audio Attenuator has an internal ramp generator which makes it ideal for switch or relay‑operated level control. In this example, the ST‑ACR1 Line‑Level Audio Controlled Relay is used to operate the RU‑VCA2 so that the activation tones sent at the start of the fire dispatch transmission are fed at reduced volume to the speakers. Full volume is reached in time for the alert message. When an alert tone is first received, the ST‑ACR1 senses audio and causes the RU‑VCA2 to ramp up the audio level. After the message is finished, the audio level is returned to minimum. The RU‑VCA2 allows front‑panel setup of both ramp up and ramp down rates. The combination of the ST‑ACR1 and RU‑VCA2 prevents random receiver noise or activation tones from bursting at full volume through the fire station sound system.

The FP‑PA20A 20 Watt Power Amplifier with 70 and 100 Volt Outputs is shown in this example.

Description:
This RDL Format‑C twisted pair system allows for the distribution of both audio and composite video over a standard CAT5 cable. This simplifies and speeds up system installation by allowing one economical cable to deliver both audio and video signals. The Format‑C sender in the data closet feeds the audio and video to receivers mounted behind each flat panel display. Twisted pair cables loop from one receiver to the next. A Format‑C distributor would allow for configurations with multiple distribution branches.

Description:
The constant voltage speaker system makes it easy to distribute audio throughout a facility. Speakers can be placed above the listeners tapped for appropriate power levels totalling up to the total amplifier capacity. The TX‑J2 is used to provide a balanced mono signal from the projector’s unbalanced stereo output. For this conference room, the FP‑PA20A constant‑voltage (70 or 100 Volt) amplifier provides up to 20 Watts RMS to speakers located directly above the seating area. The integral compressor/limiter allows high average power levels of audio free from clipping and distortion. The FP‑PA20A can be used in applications that previously would have required amplifiers rated for much higher power levels.

In this example, the amplifier is feeding four speakers at equal power levels. The 70 Volt system makes it easy to distribute audio so that clear, intelligible audio is available for all listeners.

Description:
Many projectors incorporate source switching and audio level adjustment into their remote controls. They seldom offer a high quality audio power amplifier suitable for a large boardroom or conference room. The TX‑PA40D fills that need. A stereo amplifier with integral compressor/limiter, the TX‑PA40D is capable of maintaining high average audio power levels free from clipping and distortion. There is an input switch to sum the stereo inputs for those facilities where speaker placement does not allow for good stereo imaging.

In this example, the amplifier is feeding two pairs of 8 Ohm speakers so that four speakers can be used to evenly distribute the audio throughout the room. The compact footprint of the TX‑PA40D allows it to be mounted to the projector or other convenient location. This compact, professional amplifier may be mounted in just a few square inches of space.

Description:
Waiting rooms, airport terminals, dispatch centers, and operations hubs are just a few of the locations where multiple monitors of computer generated video are needed. The EZ‑VMD4 provides one local monitor plus three monitor outputs. Outputs offer wide RGB bandwidth for superb graphics reproduction and high resolution compatibility from VGA through QXGA. Front panel switches allow ID BIT selection and selection of TTL or Video 75 Ω sync. The compact size of the EZ‑VMD4 allows the use of this professional quality distribution amplifier even when equipment space is limited.

The EZ‑VMD4 is shipped with a high‑efficiency power supply that connects to a locking dc power jack.

Description:
The EZ‑MXA20 provides a microphone preamp, mixer, limiter, tone control, and a stereo power amplifier in a package less than six inches wide. The EZ‑MXA20 handles sound reinforcement whether the audio source is a computer, CD player, live presenter or all three. The power amplifier provides 10 Watts per channel into 8 Ohm speakers or 8 Watts per channel into 4 Ohm speakers. Bass and treble tone controls provide equalization of source material. The limiter controls overloads from clipping the amplifier and an LED on the front panel of the EZ‑MXA20 indicates when the limiter is active.

Description:
In this system, a computer audio signal and a microphone signal are mixed using the RU‑MX4 Pro Audio Mic/Line Mixer. The mixed signal is distributed to multiple headphone listening stations in a language learning lab using an RU‑DA4D Audio Distribution Amplifier. Each listening station features a D‑SH1 stereo headphone amplifier, which includes an integrated level control. Each D‑SH1 is mounted in a DC‑1G desktop chassis. The DC‑1G is constructed from steel and powder coated to provide years of durability in a classroom environment. The design of the D‑SH1 headphone amplifier makes it easy to create systems with an unlimited number of headphone listening stations. Either 1/4" or 1/8" (D‑SH1M) stereo headphone jack options are available. The system design is shown in mono but stereo configurations can be implemented just as easily.