User's Manual

OSMAC Base User Manual
Page 36
Manu.01_0405
10 External Connectors
10.1 External Transceiver
The OSMAC Base may utilize an internal transceiver, an external transmitter, or an external
transceiver. A 15 pin D-sub connector is located on the rear of the OSMAC Base to facilitate
interfacing an external transmitter or external transceiver to the . The pin-out of this connector is as
follows:
External Transceiver I/O Connector Pin Out
Pin
Number
Function
1 Ground
2
B+ for the radio. Internally jumper selectable between +8V and +12V. 1 Amp
maximum current draw.
3 +8V TX. This pin floats when in the RX mode, and will be pulled to +8V when in the TX
mode. 50 mA maximum current source.
4 +5V for radio. 50 mA maximum current draw.
5 +5VRX. This pin floats in the TX mode, and will have +5V when in the RX mode. 50 mA
maximum current source.
6 TX audio. Approximately 1.7V p-p for full system deviation. 2.5V DC nominal bias on
this signal.
7 PTT out. Open collector output, pulls low to ground when the transmitter’s PA should be
on.
8 Do not use and do not connect to anything.
9 Do not use and do not connect to anything.
10 Do not use and do not connect to anything.
11 TX data out. This is the TTL POCSAG data output in the transmit mode.
12 Receiver signal strength indication input. Positive voltage represents carrier present on
channel.
13 RX audio input. 1.0V p-p for a signal with full system deviation.
14 CTCSS tone encoder output.
15 Rev E hardware and above: High when sending a POCSAG page, low otherwise.
10.2 Keyboard Connector
The OSMAC Base may be used with standard external keyboards for use with Personal
Computers that have PS-2 style connectors. Only keyboards that are fully compliant with the
two-way keyboard signaling protocol will work with the OSMAC Base. It has been found that
some brands of keyboards do not function properly with the OSMAC Base due to an incomplete
implementation of the siglnaling protocol by the keyboard.
10.3 Serial I/O Ports
The OSMAC Base has two RS-232 type serial I/O ports on it. The EIA/TIA RS-232, and the
equivalent European CCITT V.28, are electrical standards that cover the signal levels, drive level, and
slew rate of compliant devices. It is important to note that they do not specify baud rates, data
formats, or connector pin-outs. These are set by industry standards and practices.
Equipment using RS-232 ports is grouped into two categories:
DTE Data Terminal Equipment (computers, mainframes, terminals)
DCE Data Communications Equipment (modems, printers, etc.)