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RTS SPK300L
User Manual
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Telex RTS SPK300L User Manual

MODEL SPK300L TW INTERCOM SYSTEM PORTABLE SPEAKER USER STA TION
9300-3505-00 Rev F 08/2005
PROPRIETARY NOTICE
COPYRIGHT NOTICE
Customer Service DepartmentTelex Communications, Inc. (Lincoln, NE) Telephone: 402-467-5321 Fax: 402-467-3279 Factory Service: 800-553-5992
Please include a note in the box which supplies the company name, address, phone number, a person to contact regarding the repair, the type and quantity of equipment, a description of the problem and the serial number(s).
Copyright 2006 by Telex Communications, Inc. All rights reserved. Reproduction, in whole or in part, without prior written permission from Telex is prohibited.
WARRANTY NOTICE
See the enclosed warranty card for further details.
CUSTOMER SUPPORT
Technical questions should be directed to:
Customer Service Department RTS/Telex Communications, Inc. 12000 Portland Avenue South Burnsville, MN 55337 USA Telephone: 800-392-3497 Fax: 800-323-0498 Factory Service: 800-553-5992
RETURN SHIPPING INSTRUCTIONS
Shipping to the Manufacturer
All shipments of product should be made via UPS Ground, prepaid (you may request from Factory Service a different shipment method). Any shipment upgrades will be paid by the customer. The equipment should be shipped in the original packing carton. If the original carton is not available, use any suitable container that is rigid and of adequate size. If a substitute container is used, the equipment should be wrapped in paper and surrounded with at least four (4) inches of excelsior or similar shock-absorbing material. All shipments must be sent to the following address and must include the Proof of Purchase for warranty repair. Upon completion of any repair the equipment will be returned via United Parcel Service or specified shipper, collect.
Factory Service Department Telex Communications, Inc. 8601 Cornhusker Hwy. Lincoln, NE 68507 U.S.A. Attn: Service
This package should include the following:
FIGURE 1. TW System Concept Block Diagram
ii
CHAPTER 1
Introduction

DESCRIPTION

The Model SPK300L, a Portable Speaker User Station, is a component used in the TW INTERCOM SYSTEM. Each User Station is a communications unit along a multi-unit conference bus.
Figure 1, “TW System Concept Block Diagram,” on page ii, shows User Station interconnection, and User Station connection to the system power supply.
User Station interconnection can be: 1) centrally wired, with each cable coming from a central point, or 2) distributed, where all the user stations are looped together from one to another, or 3) a combination of both. The centrally wired interconnection not only reduces interchannel crosstalk, but also allows for easier expansion into an assignable channel, multi-channel system.
Figure 1, “SPK300L Block Diagram,” on page 3, shows user station functional components, input/output connections, and controls.
The SPK300L User Station has the following
functional components:
•a microphone preamplifier with limiter
•an electronic microphone switch
•a "bilateral current source" line driver
•a listen volume control
•a headphone amplifier
•a speaker amplifier
•a speaker switch
•a channel selector switch
The Microphone Preamplifier/limiter converts the small microphone signal to a strong line level signal conditions the signal strength from loud and soft talkers to be almost the same sends the signal to the line via the microphone switch and a "bilateral current source".
The Bilateral Current Source adds signal, via the channel select switch, to the line without affecting any signals already on the line. The bilateral current source also extracts the listen signal from the line and sends it to the headphone amplifier via the volume control. Some of the user's own voice signal ("sidetone") is also fed to the headphone amplifier.
1
Introduction
The Channel Selector Switch selects the channel on which the user will talk and listen. The headphone amplifier output drives the user's headphones.
The Volume Control also feeds the speaker amplifier via the speaker switch and the speaker dim network.
The User Station Voltage Regulator takes power from channel 1, regardless of the channel selector switch setting (exception: local power option units). The regulator not only supplies regulated power to the user station, but also prevents unwanted interaction between the user station and theat intercom line which is supplying the power. Because the regulator takes power from channel 1, channel 2 can be expanded into many channels by using a switch and, for each channel, a separate wire and a termination network consisting of a 200 ohm resistor and a 10 microfarad capacitor in series. (See the Application Diagrams in the TW Intercom Systems Technical Manual).
A TW System Power Supply terminates a line with 200 ohms.

Operational Controls

The SPK300L User Station has the following controls, described and shown in Section 3:
•Channel Select Switch
•Latching-action Microphone ON-OFF toggle switch.
•Momentary-action Microphone ON-OFF pushbutton switch.
•Speaker/Headphone Volume Control
•Call Switch /indicator
•Speaker ON/OFF switch
•Sidetone Adjustment

Connection, Inputs and Outputs

The SPK300L User Station has four input/output connectors:
•Dynamic Microphone type headset or handset
•Carbon Microphone type headset or handset
•Line Input (ties the station to the intercom line
•Loop/extension (allows another station to access the line through the first station. Also called loop-through.
2

Specifications

FIGURE 1. SPK300L Block Diagram
Specifications
Audio Line Voltage
Average Speech Level Range
Absolute Maximum Speech Level
Audio Line Impedance, Nominal
Nominal 32 volts DC
Operational Range
Steady state without damage
Transient 200 volts, 8 milliseconds or less (after this time, power
System DC Current
Quiescent (per station)
Dynamic (per station)
Start-Up Current
Fault Current 4.0 amperes, power supply at voltage >12 volts
1 volt, peak (0 dBm voltage-equivalent)
-20 dBV to -10 dBV
3 volts, peak (linear limit)
200 50 ohms, 75 Hz to 20 kHz System will continue to operate from 50 ohms to 300 ohms.
SYSTEM DC CURRENT
18 to 35 volts DC
-1.5 volts to 36 volts DC
supply and user station fuses will open).
10 to 40 milliamps
50 milliamps (w/25 ohm headphones) 70 milliamps (w/25 ohm headphones and lights) 100 milliamps (w/8 ohm speaker)
1.25 amperes, 50 units, all kinds
1.0 amperes, power supply at voltage <12 volts
OPERATING DISTANCES
Maximum DC limit
Maximum AC limit
System Capacitance
Input DC voltage
DC Current Quiescent, 10 to 40 milliamps
Impedance Across Line
Ambient Temperature Range
Noise Contribution to 200 ohm Line
Imput Impedence *
Source Impedance*
Maximum Input Level
Voltage Gain 54 dB
Frequency Response
5,000 ft distance along cable, power supply to single station #22 gauge wire - DC voltage drop limitation.
10,000 ft. dry pair,, power supply at each end, #22 gauge wire
0.3 microgarads (cumulative effect of 10,000 ft. of maximum cable at 30 picofarads/foot)
USER STATIONS SPECIFICATIONS
20 to 35 volts DC, operating from -200 to +36 volts DC without damage.
50 milliamps, typical (w/25 ohms headphones) 75 milliamps, typical (w/25 ohms headphones + lights) 100 milliamps, typical (w/8 ohm speaker)
10,000 ohms typical; 2,000 ohms worst case dynamic operation
Operating 0° C to 60° C (0° F to 140° F) Storage -55° C to 125° C (-67° F to 257° F)
One unit: -75 dBu Ten unit: -67 dBu
MICROPHONE PREAMPLIFIER
470 ohms
200 ohms, nominal
150 millivolts
100 Hz to 10,000 Hz, 3 dB
3
Introduction
Limiter Range 50 dB
Carbon Mic Excitation Current
Transfer Ratio 5 milliamps/1.5 volts
Output 5 milliamps into 200 ohms
Overall Voltage Gain
Overall Voltage Gain
Output Power Headset Station: 1/2 watt into 25 ohms
Frequency Response
Headphone Impedance Range
Sidetone Adjustment Range
Signaling Frequency
Flashing Rate 3Hz 2 Hz
3.468” H x 1.5” W x 3.0” D (13.21 x 3.81 x 7.62 centimeters)
10 milliamps, nominal
CURRENT SOURCE
HEADPHONE AMPLIFIER
24 dB
9 volts peak-to-peak into 25 ohms
Speaker Station: 2 watts into 8 ohms
150 Hz to 8000 Hz, 3 dB
25 to 600 ohms
20 dB to full ON
CALL LIGHT
20,000 kHz 3dB
DIMENSION
4
CHAPTER 2
INSTALLATION

MECHANICAL INSTALLATION

The Model SPK300L Portable Speaker User Station is 4.0 inches (101.6 mm) high X 8.0 inches (203.2 mm) wide X 8.0 inches (203.2 mm) deep. Additional depth should be allowed for the rear panel XLR-type line connectors. When installing this unit, allow space for control access, cabling and servicing. Provide space for: cabling service loops, reaching XLR-type connector lock releases , and headset connector/cables. If the headset connector is remotely located, allow space between this cable and interference sources such as video/TV monitors, power supplies and equipment with internal power supplies. There are no ventilation requirements.

Headset Requirements

Dynamic microphone headset type:
•50 to 1000 ohm microphone
•25 to 1000 ohm headphone(s)
High efficiency headphones are recommended because less line current is required from the power supply. Use headphones with an impedance of 25 ohms or greater. Low impedance 8 ohm headphones are not recommended. Headphones with good acoustic isolation (20 to 40dB) improve communication in high ambient noise environments, and allow the user to use the headphones at a less tiring, lower volume.
In the headset connecting cable, prevent coupling between the microphone and headphone leads by using a shielded, twisted pair for the microphone, and a separate, twisted pair for the headphones. Do not allow headphone ground to contact micro­phone ground or shield. Tie the shield to microphone ground or "mic low". The headset cable can be made longer when the microphone and headphone pairs are physically separated. The wider the separation, the longer the cable length which may be used. Estimated maximum usable headphone cable lengths are as follows:
Single cable, Two shielded twisted pair 10 ft. (3 m).
Dual ribbed cable, Two shielded twisted pair: 30 ft. (9 m).
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INSTALLATION

ELECTRICAL

Power

The SPK300L receives electrical power from either:
(1) a system power supply (26 to 32 volts DC on line connector pins 2 (+) and 1 (com) (1 or two channel operation); or
(2) a local power supply option (14 to 26 volts DC). A user station requires 18 to 33 volts to be a 10,000 ohm bridging imped­ance across the powering line, but the station can otherwise operate (as in the local power option) from 12 to 33 volts.
When using a local power supply option, each channel requires a 200 ohm load. See Figure 1-1. It is necessary to do this only once for each channel string.
Model SPK300L current requirements range from 30 to 100 mA; Since, in (1), above, the power and communications signals may share conductors, it may be necessary to overcome power losses by increasing conductor size over long runs (over 1/2 mile (804 m)). Typical operating distance for one SPK300L station is 1/2 mile (.80 km), and for one SPK300L, 1/3 mile (0.53 km) using a normal # 22 AWG conductor size.
Signal
The required number of conductors to interconnect user stations is as follows (For standard unbalanced TW user stations):
# of Channels
12 *
13 **
23 ***
*Using a TW power supply (and possibly operating on a TW system).
**Using a non-TW power supply.
***Using a TW power supply and operating on a TW two channel system.
Use shielded cable to interconnect user stations in areas of possible electrical interference, (areas such as those near: digital equipment, high current primary power conductors ("mains"), transformers, transmitters, and lamp dimmers).
Most two channel applications may use either standard microphone cable (for convenience) or two-twisted-pair cable (considerably less expensive than microphone cable). Standard wire size for the TW Intercom System is #22 gauge wire for interconnection. For permanent installations it is recommended that each channel should have individually shielded twisted pair of at least #22 gauge wire, such as Belden #8723 for 2 channels. Connect the shield to system common but do not tie the shield to chassis, earth or connector shell ground.
# of Conductors

Crosstalk Control

In the TW Intercom System all channels share a common circuit ground return. Crosstalk due to common ground resistance can be lowered by reducing the common ground resistance. Reduction of ground resistance can occur as a side benefit of using shielded cable, since the shield drains can be tied together and electrically parallel the circuit ground. Another way of lowering resistive crosstalk is to "homerun" all interconnecting cables to a central or "home" location. In this configuration, the ground path is short and the corresponding ground resistance is small. Crosstalk due to mutual capacitance occurs when the signal on one wire of a twisted pair couples into the other wire. Separating the two conductors with a shield greatly reduces the capacitive crosstalk.
To reduce both capacitive and resistive crosstalk and to afford a degree of RF and electrostatic shielding, use a cable which has a shielded twisted pair for each channel. Each pair consists of a conductor for the channel, a conductor for circuit ground return and a shield around the two conductors. The shield is accessed via a drain conductor. This drain conductor and the shield can augment the circuit grounds and thus lower the ground resistance.
6

USER STATION CONNECTIONS

Routing the TW Intercom System cables along the same ductways and pathways as power cabling can increase the noise and hum levels.

Moisture / Contamination Protection

When using equipment in the rain, always protect the equip­ment with plastic covers----also, make sure all cable con­nectors are lifted out of the mud or snow and protected with plastic bags. Water, mud and snow in connectors can cause considerable audible noise.

Hum Prevention

Prevent inducing hum into the system by not locating user stations near hum sources such as power transformers, elec­trical switch panels, lamp dimmers or TV cameras. When the microphone switch is turned on, the dynamic micro­phone acts as a sensitive antenna for hum sources.
USER STATION CONNECTIONS
Pin 3 - Channel 2
XLR-4-31/32 types (for three-Channels)
Pin 1 - Channel 1 Pin 2 - Channel 2 Pin 3 - Channel 3 Pin 4 - Common (low side of line)
Dynamic Microphone headset connector:
XLR-4-31 type receptacle (J1)
Input level: -55 dbu nominal
Output level to headphone: 10 volts peak-to-peak open circuit.
Pin 1 - Microphone low Pin 2 - Microphone high Pin 3 - Headphone low Pin 4 - Headphone high
Carbon Microphone headset connector:
Standard 1/4" Phone Jack (J2)
Input level: -15 dbu nominal
Output to Headphone: 10 volts peak-to-peak open circuit.
Tip - Carbon Microphone Ring - Headphone Sleeve - Common/ground
Line input connectors: (J3/J4)
XLR-3-31/32 types (for two-channels)
Pin 1 - Common (low side of line) Pin 2 - Channel 1
7
INSTALLATION
8
CHAPTER 3
OPERATION

Operating Controls

The table below lists the Model SPK300L operating controls. The reference numbers in the table correspond to the circled numbers in Figure 3-1.
TABLE 1. Model SPK300L Operating Controls
REF NO. NAME DESCRIPTION
1 Channel Select Switch
2 Mic ON/OFF Toggle
3 Mic ON/OFF Pushbutton
4 Volume
5 Call Light Indicator
6 Speaker ON / OFF
7 Sidetone
Selects one of two channels (standard) or one of three channels (optional). The Call Light Option transmitter and receiver operate on the channel selected by this switch. The Channel Select Switch is omitted in the Single Channel (SC) option.
A latching action switch. Turning ON the microphone slightly “dims” or attenuates the speaker.
A momentary action pushbutton switch. Not standard with the Call Light Option. Turning ON the microphone here also slightly “dims” or attenuates the speaker.
A speaker / headphone volume control. May be dual control for the Duel Listen (DL) or Program (E) Option.
CAUTION: Always turn this control all the way couterclockwise (to the left)
before plugging in the headset.
This switch / indicator appears only on the user stations with the Switch “Call Light” option. When depressed, this switch adds a 20 kilohertz signal to the TW intercom line on the same channel that the Channel Select Switch has been set. This signal activates the Call Light Receiver on all user stations which are switched to the same channel.
This switch:
turns the speaker on
1.
2. disables the headset microphone
3. enables the panel
The screwdriver adjusted SIDETONE control sets the “sidetone” level during headset operation and sets the “balance” nulling during speaker / panel microphone operation.
9
OPERATION
621 4 7 3
FIGURE 1. SPK300L Reference View
& 5

Adjust the Sidetone

To adjust the SIDETONE control for speaker operation, do the following:
1. Turn ON the speaker switch.
2. Turn ON the microphone switch.
3. Set the VOLUME control to about 50%
4. Hum into the panel microphone and adjust the SIDETONE for minimum sound through the loudspeaker.
To adjust the SIDETONE control for headset operation, do the following:
1. Turn OFF the speaker switch.
2. Turn ON the microphone switch.
3. Plug in a headset.
4. Set the VOLUME control to about 50%.
5. Turn the SIDETONE control fully counter-clockwise, then adjust it clockwise for a comfortable level of your own voice
while talking into the headset. microphone.

EN5541 - Installation, Local Power Option, RMS300 and SPK300L

The RMS300 amd SPK 300 can be powered from an external (local) power supply of between 18 to 33 volts DC. the local power option, as supplied by RTS Systems, uses a power supply assembly (RTS # 9020-4425-00), which is 117 VAC, 60 Hz in , 24 VDC 400 mA out.
To modify the RMS300 or SPK300L for local power operation, do the following:
1. Remove diode D26 from the CC300 P.C. board.
2. Add J6, 4-pin jack (Calrad #30-454, RTS # 2013-0005-00), to the back panel.
3. Wire, as shown in the diagram below. Pin 1 = common, Pin 2 = external supply + (18 to 33 VDC).
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