ZETRON 748, Technical Manual

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Installation
025-9368H 9
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
1. 9-12 VAC or +12VDC 8. Auxiliary output
2. 9-12 VAC 9. Auxiliary input
3. Power Ground 10. COR Input
4. Ground 11. Transmit Audio
5. PTT N.C. 12. TX / Gnd
6. PTT Common 13. CTCSS/DCS Output
7. PTT N.O. 14. Disc / Gnd
15. Receiver Audio
Figure 2. Model 748 Cable Connector Pin Numbers and Descriptions
INSTALLATION PROCEDURE
1. Locate the 15-Pin connector from the accessory bag included with the Model 748.
2. GROUND CONNECTION: Connect a chassis ground wire from pin 4 to the chassis ground of
the transceiver.
3. TRANSMITTER PTT: For most transmitters, a contact closure to ground will cause the
transmitter to key up. For this configuration, connect a wire from pin 7 (PTT N.O.) to the PTT
input of the transmitter. Note that this output is an open drain FET to ground.
4. TRANSMITTER AUDIO OUTPUT: Connect pin 11 (TX) to the mic or line input of the
transmitter. Shielded cable must be used for this connection. Connect the braid to pin 12
(TX/GND). Jumper JP25 determines the level of the TX Output. (A = High and B = Low)
5. CTCSS / DCS ENCODE: Connect pin 13 (SUB OUT) to the direct modulation input of the
transmitter. This wire should be shielded with the braid tied to pin 12.
6. DISCRIMINATOR INPUT: Connect pin 15 (DISC) to the discriminator output of the receiver.
Shielded cable is must be used for this connection. The shield braid should be connected to pin
14 (DISC/GND). Install jumper JP22 in position A for signals greater than 500mV P-P or in
position B for signals less than 500mV P-P. JP23 should be in the A position for CTCSS/DCS
decode and in the B position for CTCSS only decode. JP29 should be in the A position.
7. COR INPUT: The Model 748 requires a signal from the receiver to indicate when a mobile is
transmitting. This signal is derived from the receiver squelch circuit, and is sometimes called
Carrier-Operated-Relay (COR) or similar names such as RUS, CAS, or COS.
E
XTERNAL
COR
INPUT FROM THE RECEIVER
: The Model 748 needs a relay-contact closure between
Pin 10 and ground, or a voltage applied to Pin 10 that changes at least one volt between carrier
(unsquelched), and no-carrier (squelched) conditions. When the External COR wire is connected,
jumper JP21 must be in position B, and jumper JP31 will select the COR polarity; position A is for
negative (low = carrier), position B is for positive (hi = carrier) COR. Verify proper operation by
supplying, then removing a signal on the receiver RF frequency. The CARRIER LED should light
when a signal is being received. If the LED operation is backwards (off during receive, and on with