Table 2-1. Db-25 Interface Connector Pin Functions - Microwave Data Systems MDS 4310 Installation, Operation & Field Maintenance

When using an internal modem, other pin functions of the DB-25
as PTT, Receive Audio, Transmit Audio and RSSI are still active and should normally be left
open (unterminated). Connecting these pins to a computer terminal that also uses these pins
for auxiliary connections can cause improper operation.
Pin connections for the transceiver's
are described in greater detail later in this chapter.
When using the TTL interface option, external 1 kΩ (1/8 W)
pull-up resistors are required between J1 Pins 2, 3, 4, 5 & 6 and
the logic source in the remote terminal unit (RTU).

Table 2-1. DB-25 Interface Connector Pin Functions

Pin Number and Function
1. Shield
2. Transmit Data In (TXD)*
3. Received Data Out (RXD)
4. Request-To-Send (RTS)*
5. Clear-To-Send (CTS)
6. Data Set Ready (DSR)
7. Signal Ground
8. Data Carrier Detect (DCD)
9. Transmit Audio Input*
10. Receiver Unsquelched Sense
11. Receiver Filtered Audio Output
12. Radio Disable*
13. Transmit Audio Output
* Input
2-6
INTERFACE
NOTE
13
25
Viewed from Outside or from Plug's Solder Cups
INSTALLATION
INTERFACE
connector are summarized in Table 2-1 and
1
14
Pin Number and Function
14. Push-To-Talk (PTT)*
15. Transmit Clock (TC)
16. Push-To-Talk (PTT)*
17. Receive Clock (RC)*
18. +13 Vdc
19. +8 Vdc
No Connection
20.
21. Received Signal Strength Indicator
(RSSI)
22. Loopback Test–Receive Audio Input*
(For local testing of loopback DTMF
decoder)
23. Open Diagnostics
24. External Transmit Clock (ETC)*
25. Out-of-Lock Alarm
MDS 05-2415A01, Rev. A
connector, such