If block 1 in Figure T7-1 is a variable-frequency oscillator, the circuit pictured is a VFO-controlled transmitter.
If block 1 in Figure T7-1 is a crystal oscillator, the circuit pictured is a crystal-controlled transmitter.
If block 1 of Figure T7-2 is a product detector the circuit represents a simple CW and SSB receiver.
If Figure T7-2 is a diagram of a simple single-sideband receiver, the circuit shown in block 1 is a product detector.
A circuit function found in all types of receivers is the detector.
If block 1 is a frequency discriminator, the circuit pictured in Figure T7-3 is an FM receiver.
The circuit for an FM receiver uses a limiter and a frequency discriminator to produce an audio signal.
Modern HF transmitters have a built-in low-pass filter in their RF output circuits to reduce harmonic radiation.
A circuit that blocks RF energy above and below certain limits is called a band-pass filter.
A filter used in the IF section of receivers to block energy outside a certain frequency range is called a band-pass filter.
You would use a duplexer to connect a dual-band antenna to a mobile transceiver which has separate VHF and UHF outputs.