Portable telephone with external transmitter-receiver connections

A transmitter-receiver comprising:

• a transmitter;
• a transmitter circuit for converting a first audio signal to a transmit signal and transmitting the transmit signal on a first channel;
• a receiver circuit for extracting a second audio signal from a received signal on a second channel distinct from the first channel;
• a receiver;
• a jack having an output contact, an input contact, and only a single switch contact for connection to a plug of an external transmitter-receiver and wherein a switch is formed of said input contact, said output contact and said switch contact and is controlled between two states dependent on whether said jack is connected to said plug;
• a first resistor connected between one of said input contact and said output contact and a voltage source;
• a second resistor connected between said switch contact and ground;
• speaker means for generating a ringer sound;
• signal generator means for generating a ringer sound signal and supplying said ringer sound signal to said speaker means and to said output contact of said jack in response to said received signal at said receiver circuit, said speaker means generating said ringer sound according to said ringer sound signal;
• and
• control means receiving an output signal from said switch, wherein in a first state of said switch when said jack is not connected to said plug said control means supplying said first audio signal from said transmitter to said transmitter circuit and also supplying said second audio signal from said receiver circuit to said receiver according to a first DC voltage value obtained from said switch contact, and in a second state of said switch when said jack is connected to said plug said control means supplying an input audio signal from said external transmitter-receiver to said transmitter circuit through said plug and said input contact of said jack and also supplying said second audio signal from said receiver circuit to said external transmitter-receiver through said output contact of said jack and said plug according to a second DC voltage value obtained from said switch contact.

A transmitter-receiver comprising:

• a transmitter;
• a transmitter circuit for converting a first audio signal to a transmit signal and transmitting the transmit signal on a first channel;
• a receiver circuit for extracting a second audio signal from a received signal on a second channel distinct from the first channel;
• a receiver;
• a jack for connection to a plug of an external transmitter-receiver, said jack having an input contact, and output contact and only a single switch contact,
• control means controlled between two states dependent on whether said jack is connected to said plug, wherein in a first state when said jack is not connected to said plug said control means supplies said first audio signal from said transmitter to said transmitter circuit and also supplies said second audio signal from said receiver circuit to said receiver and in a second state when said jack is connected to said plug said control means supplies an input audio signal from said external transmitter-receiver to said transmitter circuit through said plug and said jack and also supplies said second audio signal from said receiver circuit to said external transmitter-receiver through said jack and said plug;
• signal generator means for generating a ringer sound signal;
• and
• speaker means for generating a ringer sound according to said ringer sound signal,
• wherein said control means in response to said received signal supplies said ringer sound signal to said speaker means and to said output contact of said jack.