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The Convex 2241A AUDIO / PTT DISTRIBUTION PANEL is used to manage “Talk Out” Audio and Push to Talk (PTT) signals bound for local or remote radios. It provides a compact means of distributing audio and Push to Talk (PTT) signals to as many as 24 base stations. In addition, it provides manual PTT override for individual transmitters. 24 front panel switches permit each radio to be keyed, disabled, or to track normal console control. Manual PTT control is used for installation and management of radio networks. It is also used to align simulcast networks by enabling one transmitter at a time to perform delay measurements.
The 2241A is packaged in a 1U high, rack mounting, panel. It is 12 Inches deep, and mounts in a 19 Inch Rack or Equipment Cabinet. At 1.7 Inches high, it takes up only one unit of vertical space.
Power options include a universal AC Supply; or 12, 24, or 48 Volt DC Supplies. All power supply options include redundant, replaceable power modules. The MAIN and BACKUP Power Modules are fused independently. In the event of a failure, a power module can be replaced with out taking the panel out of service. Section 2 has the procedure for replacing a failed power module while the 2241A is in service
Front panel LEDs indicate the status of each power module. A contact closure is provided across pins 25/50 on the Audio Output Connector to alarm in the event of a power module failure.
Distribution is configured by 7 internal switches which can be set to fan out a single input to up to 24 outputs, 2 inputs to 12 outputs, or various other configurations. The distribution switches simultaneously configure both Audio and PTT Signals
High current PTT Outputs permit direct drive of transmitters requiring up to 100 mA keying current. The Panel accepts 12 or 24 low current PTT Inputs and provides high current outputs. Two switches permit the PTT Circuits to be configured for Distribution or Buffering (Distribution OFF). The first switch controls PTT Outputs 1-12, the second controls PTT Outputs 13 -24. This arrangement permits a combination of both Distributed and Buffered PTT Circuits. That is, 12 Outputs can be set for Distribution and 12 PTT Circuits can be set to Buffer Mode. In either mode, the front panel PTT Controls are operational.
Each PTT Circuit has two independent PTT Logic Switches which select among: E/M, TTL, and Digitac Logic types. One switch (INPUT) configures the PTT Detector, and the other configures the PTT Output. PTT Logic conversion is simply a matter of selecting the desired Input and Output Logic Types.
Two switches permit each Key Detector to be set to accept a wide variety of PTT Logic Types. The INPUT LOGIC Switch selects among: E/M, TTL, and Digitac Logic types. The E/M SELECTOR provides a choice of E/M Type, or it is used to invert TTL or Digitac PTT Logic - when needed.
This three position switch selects among: E/M, TTL, and Digitac Logic types by setting the detector trip voltage and the voltage on the pull-up resistor. The purpose of the pull-up resistor is to force an idle condition if the PTT Input circuit is open or not asserted.
This two position switch selects the E/M Type or an INVERT function. Position 1 is used for Type: I, II, or III M Lead Inputs. In this position the “pull-up” resistor is connected to the detector ground and PTT is asserted when the Input is less than ( more negative ) -20 Volts. Position 2 is used for E Leads or Type IV or V M Lead Inputs. In this position the “pull-up” resistor is connected to “SB” Signal Battery / -48 Volt Input Lead and PTT is asserted when the Input is greater than ( more positive ) -20 Volts. Position 2 is also used to INVERT TTL or Digitac Logic when needed. In this case, PTT is asserted when INPUT Lead is open or high.
The 2241A can be set so that individual PTT Inputs can be distributed to multiple PTT Outputs. Two DISTRIBUTION switches control this function. The first switch controls PTT Outputs 1-12, and the second switch controls PTT Outputs 13-24. When the DISTRIBUTION Switch is ON, multiple PTT Outputs will track the state of an individual PTT Input. In this case, the PTT distribution fan-out tracks the audio distribution fan-out which is determined by the state of seven, Audio Distribution Switches. For example, if Audio Input 1 is set for distribution to Audio Outputs 1-6, then PTT Input 1 will be distributed to PTT Outputs 1-6. When the DISTRIBUTION Switch is OFF, each PTT Outputs will track the state of its individual PTT Input.
Each PTT Output circuit provides a contact closure when PTT is asserted (transmitter keyed). There is an independent, three position, PTT Logic Switch for each PTT Output Circuit. This switch which selects among: E/M, TTL, and Digitac Logic types and selects the voltage for the pullup resistor.
Each PTT Output Circuit has a PTT Override Switch located on the front panel of the 2241A. The PTT Override Switch permits manual control of PTT to facilitate installation, trouble shooting, or temporary reconfiguration of a radio system. This is a three position, lighted, toggle switch with the center position being the NORMAL setting. In the Normal Position, the PTT Output tracks the PTT Input and the switch bat lights up GREEN when PTT is asserted. In the KEY (UP) Position, the switch bat lights up RED and the PTT Output is asserted, regardless of the state of the PTT Input. In the DISABLE (DOWN) Position, the switch bat lights up RED and the PTT Output is disabled, regardless of the state of the PTT Input
Eight Audio Input Circuits are provided. These circuits are balanced and floating with a fixed 600 Ohm Input Impedance. They can be driven from a balanced or single ended source. 1-12 AUDIO INPUT / SUM Circuits.
Eight Audio Input Sum Circuits are provided. These circuits are primarily used to sum (voted) receiver audio with transmit audio. They are balanced and floating and have an Input Impedance Switch. This switch is set to HI Z ( 20 K Ohms) when the sum input is paralleled with (bridging) another 600 Ohm Input. It is set to 600 Ohms when the sum input is used to terminate a circuit, or when the Sum Input is not in use. 1-13 AUDIO OUTPUT C
There are 24 Audio Output Circuits. These circuits are balanced and floating with a fixed 600 Ohm Output Impedance. They can be terminated with a balanced or single ended load. The (Input to Output) gain of the audio circuits is factory set to unity / 0.0 dB. However, a front panel, screw adjustment, GAIN CONTROL is provided for normalizing transmitter deviation. This control has a range of +/- 10 dB (0.316 to 3.16) with a logarithmic characteristic that provides a constant dB gain change per degree of rotation. Use of 15 turn potentiometers provides high resolution control.