Mueller Broadcast Design


T25-35SA Installation Instructions

Wiring Connections:

All connections to the T25-35SA are made via the DB-9M connector on the rear panel. We supply the mating connector for this. The pin diagram below may help you identify which holes are which, and they are printed (in very tiny numbers) on the shell itself.

    1    Audio Input +
    2    Audio Input -
    3    Audio Ground
    4    Audio Output -
    5    Audio Output +
    6    25 Hz + 35 Hz Closure
    7    35 Hz Closure
    8    25 Hz Closure
    9    Closure (relay) common w/6, 7 & 8

Audio input connections are made to pins 1 (+) and 2 (-). If you are using an unbalanced input then connect the "hot" lead to pin 1 and the ground to pin 2.

Audio output connections are made to pins 4 (-) and 5 (+) for balanced output or pins 3 (GROUND) and 4 (-) for unbalanced output. DO NOT CONNECT GROUND TO EITHER PIN 4 OR 5. Leave the unused pin disconnected. Note: Early units have unbalanced outputs and pin 5 is not connected.

Control output connections are made on pins 6, 7, 8 and 9. Pin 9 is the relay contact common. Pin 8 closes to pin 9 on 25 Hz alone, pin 7 closes to pin 9 on 35 Hz alone, and pin 6 closes to pin 9 on 25 Hz and 35 Hz together.

The only "ground" connection to the electronics in this unit is through pin 3. If you experience noise or RF interference connect pin 3 to your shield ground. The third prong "safety ground" on the line cord is only connected to the metal chassis. The four relay contact closure pins are isolated from all other circuits.

Initial Checkout:

Once your audio and control connections are made, apply power to the unit. The front panel LED's show the status of the unit. The two green LED's (+12 volts DC and - 12 volts DC) indicate whether the voltage regulators are working. The two red LED's (25 Hz Detect and 35 Hz Detect) light whenever the unit detects the subaudible tone(s). The yellow Output Pulse LED lights when the unit is issuing a pulse to one of the three "Pulse" outputs. At this point, with no audio input, only the two green power supply LEDs should be lit.

As shipped, this unit expects a 0 dBm (600 ohms) nominal input level. If your input levels are higher or lower than this, remove the cover (there are two screws on each side of the enclosure) and check the LEVEL CHECK LED on the circuit board. Under normal conditions, with program material present, this LED should be green with red flashes. It should not go dark except during program pauses of two seconds or more. If it is dark most of the time, or never flashes red, turn the INPUT LEVEL control clockwise until this condition is observed. If the LED is red all the time or just occasionally flashes from red to green, turn the INPUT LEVEL control counter- clockwise. This is the only adjustment necessary for proper operation. If everything is adjusted properly, the nominal output level should be 0 dBm.

Normal Operation:

This unit will detect any 25 Hz and 35 Hz audio frequencies which are present in the program material. Several safeguards have been designed into the unit to prevent false tripping. The red Detect LED must stay lit until the yellow Output Pulse LED lights in order to get a pulse output. The state of the detector is latched at the moment the yellow LED lights and any further changes in the state of either the 25 or 35 Hz detectors is ignored. Under certain conditions, a brief trip of either detector will cause the yellow light to flash, but the Detect LED usually goes dark before the output is latched. In this case, there will be no pulse output given by the unit. In order to cause an output pulse, the tone must be present for at least 1/4 second. An occasional flicker of the Detect lights (especially the 35 Hz LED) is normal if the network programming contains significant low frequency components and the network is not properly high-pass filtering the program audio. This can also occur if impulse noise ("pops") is present on your satellite audio.

The normal sequence for a valid tone is (1) DETECT LED lights, (2) 250 millisecond delay, (3) OUTPUT PULSE LED lights / Relay Contact Closure issued for approximately 250 milliseconds, (4) RESET, ready for next tone, red and yellow LEDs dark. This final step will not occur until tones are no longer present.

Some satellite receivers have a high-pass filter in the audio path or have poor low frequency response characteristics. Switch out any high-pass filtering if your receiver has it. It will suppress the 25 Hz and 35 Hz tones in the program audio. This unit cannot compensate for poor audio response, but if the tones are present, an additional sensitivity adjustment may recover the tones if they are not too far "down".

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Mueller Broadcast Design
613 S. La Grange Rd. , La Grange, IL  60525
Phone: (708) 352-2166

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