EFJohnson 761X, 764X UHF I/O Expander IC12 Main Unit, UHF Port Expander IC13 Main Unit

UHF (7640) CIRCUIT DESCRIPTION

Pin	Port	Description
No.	Name
51	BM	Outputs control signal for beep mute cir-
		cuit Q10. High = Beep muted.
52-	CTDA0-	Output port for CTCSS/DTCS signals.
54	CTDA2
55	HANG	Input port for the microphone hanger
		detection signal. Low = Microphone on
		hook.
90	MTONE	Output port for beep audio while receiving
		and 2/5 tone signals while transmitting.
91	TONED	Outputs DTMF signals.
94-	OPV3-	Input port for option connector J4 state
96	OPV1	(main unit).
97	CTCIN	Input port for the CTCSS/DTCS IN
		decode signals.
98	SD	Input port for S-meter signal.
99	LVIN	Input port for PLL lock voltage.
100	TEMP	Input port for the transceiver’s internal
		temperature.

5.7.5 UHF I/O EXPANDER IC12 (MAIN UNIT)

Pin	Port	Description
No.	Name
2, 3,	T1-T3	Output tunable bandpass filter control
10		signals.
11	T4	Output port for tunable bandpass filter
		control signal while receiving and power
		control signal while transmitting.
14	REF	Output port for reference frequency
		control voltage.

5.7.6 UHF PORT EXPANDER IC13 (MAIN UNIT)

Pin	Port	Description
No.	Name
4	TXC	Outputs control signal for R8 regulator
		Q10/Q11 (main unit). High = Transmit
		mode.
5	TMUT	Outputs control signal for T8 regulator
		Q8/Q9 (main unit). High = Transmitter
		off.
6	RM	Outputs AF mute switch IC11(main unit)
		control signal for the receiver circuit. High
		= No receive audio is emitted.
7	MM	Outputs MIC mute control signal. High =
		DTMF signals are output, etc.
11	HORNO	Outputs external device control signal.
		High = Matched 2/5-tone signals are
		received.
12	AFON	Outputs control signal for the AF amplifier
		regulator circuit. High = Squelch is open,
		etc.
13	AFHPF	Outputs AF filter control signal. High =
		Filter out CTCSS or DTCS frequency.
14	NWC	Outputs receive/transmit passband width
		control signal. High = Narrow bandwidth
		is selected.

November 1998
Part No. 001-7600-001	5B-12