Priority Audio Switch - 2 in and 1 out with priority keying - PAS

Industrial rated -25 to +65 C Two audio ports in, a primary and secondary... one audio port out Uses E&M or 600 ohm line audio levels PTT (switch closure) on primary input overrides secondary audio input 48 VDC relay controlled (other control voltages by special order) Rack Mount Option Available Ideal for small dispatch radio operations with multiple control points Each unit contains two identical switch instances of 2 in by 1 out Switches both audio leads for balanced or unbalanced audio circuits

The PAS switches both sides of the audio circuit, so it may be used with either balanced or unbalanced audio sources. The PTT leads are contact closures. The PAS switches the PTT and audio using relays with 48VDC power. Other input power voltages are available by special order.

While initially designed for use with audio carried over telco 4-wire E&M remote circuits, it also works well with standard audio and PTT consoles.

The Priority Audio Switch has 2 completely isolated instances of the priority switching function that may be used independently with two transmitters or cascaded for a three-input single transmitter configuration.

There is an internal jumper for each audio pair to provide either an internal ground connection or ground connection from the attached input device. For example, if a radio attached to the output side of the PAS has voltage on the PTT lead when it is activated, the internal ground connection is used to insure the radio PTT voltage does not continuously hold the relay in the priority position.

How it works...
For a typical installation using 4-wire E&M circuits, the Priority Audio Switch takes in two 4-wire E&M lines with the M-lead for switch control. The ports are paired as Priority and Secondary. The “Priority” will seize control of the audio channel when the E-lead into the PAS turns on. The E-lead input is the M-lead output of a channel bank set to A-Side wiring. The E-lead input can also be a Push to Talk (PTT) lead directly from a radio.

If the Secondary port is talking through the E&M transmit pair and the Priority port asserts the M-lead, Priority seizes the transmit pair. The PAS has 2 pairs of Priority/Secondary ports. Therefor, there are 2 independent input port pairs.

Received audio is broadcast back out both the Primary and Secondary ports.

The M-lead input is a closure to chassis ground on the channel bank. The power input to the Priority Audio Switch is 48 volts DC supplied externally from the channel bank power supply. When the M-lead from the channel bank closes for port 1, 48 volts is applied to the switch, which cuts off the transmit audio of port 2 and switches the audio path to port 1.

SPECIFICATIONS

General

• Four audio input ports, 2 sets of 2 in by 1 out pairs with priority
• RJ45 connectors
• E&M M-lead control input on pin 2
• Audio priority control via M-lead
• Receive audio is broadcast back to both input ports
• Two pairs of controlled Priority/Secondary ports

Physical/Electrical

• Power requirements: 48VDC
• 5 ¼”x 5 ½”x 1 ¾”
• One pound

Environmental

• Operational Temperature: -25 to +65 C
• Humidity: Non-condensing

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