Barnett Engineering B1474 Setup Procedures, Remove The Top Cover, Connections Line Interface

5 SETUP PROCEDURES

The semiconductors can be damaged by static discharge. Proper handling procedures must be followed. Do not touch any of the devices inside the modem, and work only in a static free, clean, and dry environment.

(1) Remove The Top Cover

Remove the two center screws on the top cover of the modem to release it from the base. Pull straight up on the cover to expose connections and internal DIP switches.

(2)CONNECTIONS Line Interface

Connect the audio wires in accordance with the configurations below:

4 wire cable: Connect the two transmit wires into pins 4 and 5 of P1. The receive wires con- nect into pins 7 and 8 of P1. SW3.3 and SW3.4 must be OFF.

2 wire cable: Connect the two wires into pins 4 and 5 of P1. Ensure that SW3.3 and SW3.4 are ON.

Radio

If the radio is equipped with a 600 ohm balanced interface, connect the transmit and receive audio lines as shown above for a cable interface.

For a single-ended radio interface, connect P1-3 to the transmit line of the radio and P1-6 to the receive line. Connecting the receive input to an unsquelched source in the radio will result in extraneous characters at the data port, unless the squelch detector is set properly.

PTT: The B1474 provides an open collector driver for the radio PTT at P1-10.

Squelch: The radio’s receive carrier operated switch (COS) can be monitored to detect when the radio is receiving a signal by connecting the COS line to P1-7. This sig- nal is used to inhibit transmissions over a busy channel.

The input is capable of monitoring a level from 0 to 10 VDC.

See “Squelch Polarity” under DIP switch settings to set the COS polarity and level, or to disable this feature.

If using the Option 002 trunking software, connect the radio’s RFCTS into the squelch input.

Digital Connection

A DB-25S socket on the side of the unit is used to interface with the computer equipment.

The RS232 interface provides a DCE interface using the following signals:

B1474 BARNETT ENGINEERING LTD. PAGE 12