a telephone in accordance with the present invention allows the user to simultaneously use the handset and hand - free functions . as illustrated in fig2 the telephone comprises a keyboard 10 , which comprises a plurality of push buttons including spkr / swap button , line1 button , line2 button , hold button , 2tel button , and conf button . line1 button and line2 button represent two different telephone lines . hold button holds the connected telephone line in communication . conf button is a conference telephone function control button . 2tel button is to select if let hand - free circuit and talking circuit be respectively operated at the same time or not . swap button is used to switch between handset function and hand - free function . the keyboard 10 further comprises rls1 button and rls2 button for hanging up line1 and line2 respectively . the keyboard 10 is connected to a cpu ( central processing unit ) 20 . the cpu 20 is connected with a first ringing circuit 30 and a second ringing circuit 40 . the first ringing circuit 30 and the second ringing circuit 40 are respectively connected to a first telephone line 50 and a second telephone line 60 . the first telephone line 50 and the second telephone line 60 are respectively connected to the external exchange line . a first switch ( k1 ) 70 is installed in a line , which is connected between the first telephone line 50 and the second telephone line 60 . the first switch ( k1 ) 70 is also connected to the cpu 20 . through the cpu 20 to switch on / off the first switch ( k1 ) 70 , the telephone lines 50 and 60 are closed / opened . a second switch ( k2 ) 51 and a third switch ( k3 ) 61 are respectively installed in the first telephone line 50 and the second telephone line 60 . the second switch ( k2 ) 51 and the third switch ( k3 ) 61 are respectively formed of a relay ( any equivalent element may be used ). the input end of the second switch ( k2 ) 51 is connected to the first telephone line 50 . the input end of the third switch ( k3 ) 61 is connected to the second telephone line 60 . the first contact 511 of the output end of the second switch ( k2 ) 51 and the second contact 612 of the output end of the third switch ( k3 ) 61 are respectively connected to a talking circuit 80 . the second contact 512 of the output end of the second switch ( k2 ) 51 and the first contact 611 of the output end of the third switch ( k3 ) 61 are respectively connected to a hand - free circuit 90 . the second switch ( k2 ) 51 and the third switch ( k3 ) 61 are also respectively connected to the cpu 20 , so that the cpu 20 can connect the first telephone line 50 or second telephone line 60 to the talking circuit 80 or hand - free circuit 90 through the second switch ( k2 ) 51 or third switch ( k3 ) 61 . a fourth switch ( k7 ) 81 is connected between the talking circuit 80 and the second switch ( k2 ) 51 . a fifth switch ( k8 ) 91 is connected between the hand - free circuit 90 and the third switch ( k3 ) 61 . the fourth switch ( k7 ) 81 and the fifth switch ( k8 ) 91 are respectively formed of a triode ( any equivalent element may be used ). the fourth switch ( k7 ) 81 and the fifth switch ( k8 ) 91 are respectively connected to the cpu 20 . further , the first telephone line 50 and the second telephone line 60 are respectively connected to a first load - circuit 52 and a second load - circuit 62 . a sixth switch ( k4 ) 53 and a seventh switch ( k4 &# 39 ;) 63 are respectively installed in the first load - circuit 52 and the second load - circuit 62 , and respectively connected to the cpu 20 . therefore , the cpu 20 can control the sixth switch ( k4 ) 53 and the seventh switch ( k4 &# 39 ;) 63 , enabling the talking circuit 80 and the hand - free circuit 90 to be held when the sixth switch ( k4 ) 53 and the seventh switch ( k4 &# 39 ;) 63 are closed . when the sixth switch ( k4 ) 53 and the seventh switch ( k4 &# 39 ;) 63 are broken , the load - circuits 52 and 62 are released , enabling the talking circuit 80 and the hand - free circuit 90 to be reset . the cpu 20 comprises a dtmf generator 21 connected to the input end of an eighth switch ( k6 ) 22 . the first contact 221 and second contact 222 of the output end of the eighth switch ( k6 ) 22 are respectively connected to the talking circuit 80 and the hand - free circuit 90 . therefore , signal from the dtmf generator 21 is sent through the eighth switch ( k6 ) 22 to the talking circuit 80 or hand - free circuit 90 . referring to fig2 again , when the first ringing circuit 30 is triggered to output a signal ring1 , line1 flashes , informing an user ( hereinafter called as person a ) of a telephone call from a caller ( hereinafter called as person b ) at the first telephone line 50 . when person a picks up the handset , the hook release circuit ( not shown ) produces a signal hook , and sends the signal hook to the cpu 20 . upon receipt of the signal hook from the hook release circuit , the cpu 20 produces control signals swctl and hkctl . the control signal swctl is sent to the second switch 51 , causing the input end of the second switch 51 to be connected to the first contact 511 at the output end of the second switch 51 , and the input end of the third switch 61 to be connected to the first contact 611 at the output end of the third switch 61 . the control signal hkctl is sent to the fourth switch 81 , causing the fourth switch 81 to be closed . therefore , person a and person b can talk to each other through the talking circuit 80 . when the second ringing circuit 40 is triggered to output a signal ring2 during conversation between the first party and the second party , line 2 flashes , informing another user ( hereinafter called as person d ) of a telephone call from a caller ( hereinafter called as person c ) at the second telephone line 60 . person d can then push the button 2tel . when the button 2tel is pressed on , the cpu 20 is driven to output a control signal hfctl to the fifth switch 91 , causing the fifth switch 91 to be closed . thus , person c and person d can talk to each other through the hand - free circuit 90 during conversation between person a and person b , i . e ., the talking circuit 80 and the handfree circuit 90 are independently used at the same time . when person a and person b talks to each other through the talking circuit 90 , person c and person d talks to each other through the hand - free circuit 90 , the button hold can be depressed to drive the cpu 20 to output signals load1 and load2 to the sixth switch 53 and the seventh switch 63 , causing the sixth switch 53 and the seventh switch 63 to be closed . when the sixth switch 53 and the seventh switch 63 are closed , the first telephone line 50 and the second telephone line 60 are respectively connected to the load - circuits 52 and 62 , enabling the telephone lines to be maintained in communication . the button spkr / swap is then depressed to drive the cpu 20 to output signals swctl , load1 and load2 . the signal swctl is sent to the second switch 51 , causing the input end of the second switch 51 to be switched from the first contact 511 at the output end of the second switch 51 to the second contact 512 at the output end of the second switch 51 , and the input end of the third switch 61 to be switched to the second contact 612 at the output end of the third switch 61 . the signal load1 and the signal load2 are respectively sent to the sixth switch 53 and the seventh switch 63 , causing the sixth switch 53 and the seventh switch 63 to be switched off . when the sixth switch 53 and the seventh switch 63 are switched off , the load - circuits 52 and 62 are released , and the talking circuit 80 is reset , therefore person a and person b can talk to each other through the hand - free circuit 90 , person c and d can talk to each other through the talking circuit 80 . further , for a four - party conference , the button conf is depressed to drive the cpu 20 to output a signal conf to the first switch 70 , causing the first switch 70 to be closed , and therefore the four persons are allowed to make a telephone conference . in order for further understanding of the present invention , an application example is described hereinafter . when person c calls person d through the other telephone line during a talk between person a and person b through the handset , person d immediately presses on button 2tel at the keyboard 10 so as to communicate with person c through the hand - free circuit 90 . if person a and person b do not want other to hear their conversation , person a can press on button hold and button 2tel so as to talk to person b through the hand - free circuit , leaving person c and person d to talk to each other through the talking circuit 80 . if person a , person b , person c and person d wish to make a conference , button conf at the keyboard 10 is depressed . it is apparent that although the invention has been described in connection with the preferred embodiment , it is contemplated that those skilled in the art may make changes to the preferred embodiment without departing from the scope of the invention as defined in the appended claims .