JPH01255352A - Telephone system having holding transfer function - Google Patents

Abstract

PURPOSE:To easily realize a call between plural persons to contain even a holding transfer source by controlling a switching circuit part so as to connect a transfer destination call slave set, a holding source call slave set and other call slave sets in the middle of holding under conditions that the transfer destination call slave set executes a secret call releasing operation. CONSTITUTION:At the time executing the pending operation of a call when a telephone slave set 12 executes the call with a trunk line or the other telephone slave set 12 and a door phone 13, a control circuit 16 sends a holding melody to the trunk line, the other telephone slave set 12 or the door phone 13 to be held. Further, by the transfer operation of the holding source call set 12, the trunk line, the other telephone slave set 12 or the door phone 13 in the middle of holding is transferred to the other new telephone slave set 12, and when the transfer destination telephone slave set 12 executes the secret can releasing operation at such a time, a switching circuit part 31 is controlled so that even the telephone slave set 12 of the holding transfer source can participate in the call after the transfer. Thus, the call between plural persons to contain even to the holding transfer source can be easily realized.

Description

[Detailed Description of the Invention] [Industrial Application Field] What is the present invention? The present invention relates to a telephone device that is equipped with a plurality of telephone handsets such as FT handsets and door phones and has a hold transfer function.

[Prior Art] A telephone device such as a home telephone has a main telephone circuit connected to nine office lines, and a plurality of telephone handsets each connected to the main telephone circuit via a telephone line. It is conceivable to use one that has a doorphone connected via the door phone.

On the other hand, in conventional telephone equipment equipped with a plurality of telephone handsets, when the telephone handset performs an operation to put the call on hold during an outside line call with a central office line, it sends a certain voice melody to the held central office line. There is a system that allows a station line on hold to be transferred to another telephone handset by performing a transfer operation on the holding telephone handset.

[Problems to be Solved by the Invention] However, in the conventional telephone device, during a call between Party A and Party B, Party A puts Party B on hold through a hold operation, calls Party C through a transfer operation by Party A, who is on hold, and puts Party B on hold. When the transfer of the middle party B to the above C is completed, the party A who performed the hold transfer operation cannot participate in the call between the transferred party B and C.

Although this is useful when it is necessary to keep the call between Party B and Party C confidential to Party A, who is the hold transfer source, it is also useful if the call between Party A and Party C includes Party A, who is the hold transfer source. There is an inconvenience in that it makes it impossible to make inter-communication calls.

The present invention allows the transfer destination party to select whether or not to keep the call confidential to the hold transfer source after the call is held and transferred, and the hold transfer source The purpose of the present invention is to make it possible to easily realize multi-party telephone calls, including communications between multiple parties.

[Means for Solving the Problems 1] The present invention provides a main telephone circuit connected to a single central office line, a dual telephone handset connected to the main local telephone circuit via telephone lines, and a main telephone circuit connected to the main telephone line. A telephone device comprising a control circuit for driving and controlling the circuit, wherein the main telephone circuit is equipped with a hold signal generator, and an exchange connection between a central office line and a telephone handset; It is equipped with an exchange circuit section that can perform 6 exchange connections between the handset and the hold signal generator, and the control circuit is as follows:
When a telephone handset performs a hold operation for the call during an extension call with another telephone handset, connect the signal generator to send a hold signal to the other telephone handset, ■When the above-mentioned holding calling handset performs a transfer operation to another new calling handset, the forwarding destination handset generates a discharge sound, and the transferred calling handset responds to the call and the holding calling handset transfers to another new calling handset. After establishing the call status with the device, ■ is transferred to the forwarding destination handset, the holding source handset, and the other handset on hold, on the condition that the forwarding destination handset performs a deprivation operation. The switching circuit section is controlled so as to connect the switching circuit.

[Function] According to the present invention, when one call handset (telephone handset, doorbell, etc.) performs a hold operation for a call during a call with a central office line or another telephone handset, the held central office line or other handset In addition to sending a hold signal to the call handset, the station line or other call handset on hold can be further transferred to another call handset by the transfer operation of the hold originating call handset. At this time, if the transfer destination call handset performs a deprivation operation, the hold transfer source call handset can also participate in the transferred call.

In other words, the transfer destination party can select whether or not to keep the call confidential to the hold transfer source after the call has been transferred to hold. It is possible to easily realize multi-party calls including:

[Embodiment] FIG. 1 is a circuit diagram showing a telephone device according to an embodiment of the present invention, and FIGS. 2 to 7 are flowcharts corresponding to various operating modes of the telephone device.

Telephone device? Reference numeral 110 denotes a main device 11, a plurality of telephone handsets 12 (in this embodiment, five telephone handsets 1 to 5), and a plurality of telephone handsets 12 (in this embodiment, first to third door phones). The system consists of 3 door phones (3 door phones) and 13 door phones.

The main device ttt includes a main telephone circuit 15 and a control circuit 16.
and a power supply circuit 17.

The main telephone circuit 15 is connected to the office lines 18A and 18B, and is connected to each telephone cordless handset 12 with two telephone lines 19A and 19A, respectively.
19B, each door phone 13 and 2
They are connected by wooden communication lines 20A and 20B.

The main telephone circuit 15 includes a ringing signal loop detector 21, a DTM
F oscillator oscillator 2 sending 1 signal generator) 23, hold signal generator (melody IC)
24, :I7 capacitor c1. Resistor R1, relay rll
, r12, ) is equipped with a lance tl and a capacitor c2.

In addition, the main telephone circuit 15 is connected to each telephone handset 12 (112 to 5).
12), the calling signal oscillator 2
B (126-526), off footer detection n27 (12
7-527), extension loop detector 28 (128-52
8), PR receiver 29, capacitors c13 to c53,
c14-c54, relay r 13-r 53. r
14~r 54, battery bll~b51, transformer t
12 to t52.

In addition, the main telephone circuit 15 is connected to each door phone 13 (113 to 3).
13), door phone FB press detector 30 (130 to 330), relay rol to r
It is equipped with 03.

The main telephone circuit 15 also includes a crosspoint circuit (switching circuit section) 31 consisting of a crosspoint IC.

The cross point circuit 31 has seven horizontal lines "O" to "B" and four vertical lines "A" to "D" arranged orthogonally to the phase W. The "0" line is a door phone exchange circuit, and relays r01 to r03 of each door phone 13 are connected to the "0" line via a bidirectional amplifier circuit 32. Lines “1” to “5” are the communication circuits for each telephone handset, and lines “1” to “5” are the lines opposite to the telephone handset of each transformer t12 to t52 corresponding to each telephone handset 12. The terminals are connected. The "8" line is a hold circuit, and the "B" line is connected to a hold signal generator ?4.
The "A" line is a station line circuit, and the opposite terminal of the transformer kl is connected to the "A" line. The "B" line is an extension circuit. The "C" line is a holding circuit. The "D" line is an interrupt circuit, and the interrupt signal oscillator 23 is connected to the "D" line.

The cross point circuit 31 turns on/off the contact state of the cross points (indicated by Δ in FIG. 1) of each horizontal line and each vertical line in L by the control circuit 16, and connects each telephone terminal 112 to the outside m<
Exchange connection to the central office line), extension line, doorbell, hold, and interrupt circuits. In addition.

The cross point (C, 6) indicated by mu in FIG. 1 is in the always-on IE.

The control circuit 16 includes a ring detector 21 of the main telephone circuit 15, an off-hook detector 27 (127 to 527),
Extension loop detector 28 (128-528), PB receiver 29. Door phone PR press detector 30 (130-33
0). The control circuit 16 includes 4
- Based on the reception results of each transmission signal, the crosspoint circuit 31. DTMF oscillator 22. It drives and controls the relays r01 to r03 of each door phone 13, the hold signal generator 24, etc.

Each telephone handset 12 has a telephone circuit 34 and a power supply circuit 35. The telephone circuit 34 includes a dial circuit section, a telephone call circuit section, and a ringer circuit section.

Various operating modes of the torpedo device 10 will be explained below.

(Call an outside line...see Figure 2) When attempting to make an outside call using the telephone handset 12, for example, the first telephone handset 112, the handset of the first telephone handset 112 is placed on standby. When going off-hook from the state, the extension loop detector 28 corresponding to the 11th rL handset 112 sends this off-hook information to the control circuit 16. Control circuit 16
is the cross point (A, l) of the cross point circuit 31
By turning on and moving relay rll toward transformer kl, an outside line transmission mode is established. First telephone handset 11
2 dials the destination number, the first telephone number is 112.
The extension loop detector 28 (when the dial information is a dial pulse signal) or the PB receiver 29 (when the dial information is a button signal t;) corresponding to the dial information is sent to the control circuit 16. When the control circuit 16 sends a dial pulse signal to the central office line, the control circuit 16 connects relay rll to
A dial pulse is transmitted to the office lines 18A and 18B by turning on/off the dial pulse, and at this time, relay r12 is used to shunt the dial pulse to prevent pulse noise from being transmitted to the telephone handset 12 when dialing. (2) When sending a button signal to the office line, this dial information is transmitted to the DTMF oscillator 22, and a tone is transmitted from the oscillator 22 to the office lines 18A and 18B. When the ringing signal loop detector 21 detects a reversal of the central office line due to the off-hook of the telephone handset of the other party, this detection information is sent to the control circuit 16, and an outside line communication state is established.

(Incoming outside line call...see Figure 3) When a calling signal from the office arrives on the office lines 18A and 18B,
The ring signal loop detector 21 detects the arrival of an outside line, and this detection information is sent to the control circuit 16. The control circuit 16 is
In this embodiment, the relays r13 and r23 corresponding to the first telephone handset 112 and the second telephone handset a212, which are set in the priority order of outside line calling, are switched to the ringing signal oscillator 26,
relay r14. r24 is switched to the off-footer detector 27, and the first telephone handset 112 and the second telephone handset 212 are made to ring. The control circuit 16 counts the number of rings of the first telephone handset 112 and the second telephone handset 212, and each off-hook detector 2
7 sends on-hook/off-footer information of these telephones fi12 to the control circuit 16.

■If the first telephone handset a112 or the second telephone handset 212 responds within 5 rings, the control circuit 16 is connected to the L/-
r13. r23, and relay r14゜r24, ■ the first telephone handset 112 or the second telephone handset a1
212 does not respond within five rings, the control circuit 16 switches the relays r33 to r53 corresponding to the other third telephone handset 312 to fifth telephone handset 512 to the ringing signal oscillator 26, and switches the relays r34 to r34 to the ring signal oscillator 26. r54 off hook detector 27
, the other telephone handsets 12 also ring, and the third telephone handset 1
1312 to the fifth telephone 41512 (detected by the on-hook/off-hook information of the off-hook detector 27), the relays r33 to r53. and relay r
34 to r54 are restored.

Next, the control circuit 16 moves the relay rll toward the transformer tl! For example, if the second telephone handset 212 is off-hook and in a response state, the cross point (A, 2) of the cross point circuit 31 is turned on to establish an outside line communication state.

(Extension call...see FIG. 4) When attempting to make an extension call using any telephone 812, for example, the fifth telephone 512, when the handset of the fifth telephone handset 512 is off-hook from the standby state, 5th telephone Ia5
An extension loop detector 28 corresponding to 12 sends this off-hook information to control circuit 16. The control circuit 16 turns on the cross point (A, 5) of the cross point circuit 31 and turns the relay rll toward the transformer tl.

The fifth telephone handset 512 forms the outside line calling mode.
When the telephone dials "0", the extension loop detector 28 corresponding to the fifth telephone handset 512 sends this dial information to the control circuit 16. Then 3 seconds (preset)
If there is no dial information, the control circuit 16 connects relay rll.
to the capacitor cl, cross point circuit 31
Cross point) (D, 5) is turned on/off to send an extension dial tone to the fifth telephone handset 512, and cross point) (A, 5) is turned off to form an extension dial mode. , the fifth telephone handset 512 calls the called number Jl (1
4), the extension loop detector 28 corresponding to the fifth telephone fi 512 sends this dial information to the control circuit 16. The control circuit 16 is connected to the called telephone handset 12.
The extension loop detector 28 detects the called telephone handset 1.
Obtain on-hook/off-footer information for 2.

The control circuit 16 switches the relay R3 corresponding to the called telephone handset 12 to the ringing signal oscillator 26, and switches the relay R14 to the off-hook detector 27, if the called telephone handset 12 is in the on-hook state; The called telephone handset 12 rings and the cross point (D,
5) to send a ring tone to the fifth telephone handset 512, and if the called telephone handset 41112 is in an off-hook state, the crosspoint (D
, 5) is turned on/off to send a busy tone to the fifth telephone handset 512, and the fifth telephone handset 1a512 dials another called number. After executing the above step (2), the control circuit 16 obtains the on-hook/off-book information from the off-hook detector 27, and (3) switches the relay r of the called telephone handset 12 when the called telephone handset 12 goes off-hook. For example, when the first telephone fil12 responds, the cross point (D, 5) of the cross point circuit 31 is restored.
), cross points (B, l), (B.

5), and establish an extension call state. ■If the called telephone handset 12 does not go off-hook and does not respond.

The fifth telephone unit a512 can call another telephone handset by dialing another destination number.

(Door phone call...see FIG. 5) When attempting to make a door phone call using any door phone 13, for example, the first door phone 113, the door phone PB press detector 30
Press button information of the door phone 113 is sent to the control circuit 16. The control circuit 16 switches the relays r13 to r53 corresponding to all the telephone handsets 12 to the ringing signal oscillator 26, and switches the relays r14 to r54 to the off-hook detector 27, thereby calling all the telephone handsets 12 at once and causing them to ring. . The control circuit 16 obtains on-hook/off-hook information from the off-hook detectors 27 corresponding to all telephone handsets 12, and monitors whether there is a response within three rings.

■If the control circuit 16 receives a response within the above three beeps,
While restoring relays r13 to r53 and relays r1.4 to r54 corresponding to all telephone handsets 12 and turning on relay rot, for example, when the second telephone handset 212 responds by going off-hook, the cross point circuit 31 cross points (B.

0), (B, 2) to establish a doorbell call state.

(2) If there is no response within the above-mentioned three rings, the control circuit 16 sends the relays r13 to r53 corresponding to all the local handsets 12.
And restore relays r14 to r54 and ring +LL,
(1) If any telephone handset 12 responds within those few seconds, a doorbell call letter IE is established in the same way as in (2) above, and (2) any telephone handset 12 responds within those few seconds. If not, it will be in a standby state.

(Hold Transfer...See Figure 6) Any - [When the crystal handset 12, for example, the fifth telephone handset 512 is in the state of an outside line call, an internal call, or a doorbell call, the telephone handset 12 is set to "0". ”When you dial, the corresponding telephone T-machine 1
The extension loop detector 28 corresponding to 2 sends this dial information to the control circuit 16, and the control circuit 16 detects the corresponding cross point) (A) on the hold circuit of the cross point circuit 31.
, 6), (C, O) to (C, 5) to output the hold melody of the hold signal generator 24 to the fifth telephone handset 51.
The crosspoint (A, 5) or (B) was sent to the other party on hold who was in the conversation state with 2, and the crosspoint circuit 31 was in the on state.

5) is turned off (suspended), the control circuit 16 turns on/off (D, 5) of the cross point circuit 31 to turn off fR5.
An extension dial tone is sent to the telephone handset 512.

Next, when the fifth telephone handset 512 dials the forwarding destination number 1 (1 to 4), for example, the first telephone handset as the forwarding destination is dialed in the same way as in the extension call mode of FIG. ! 2
An extension call state (crosspoints (B, 1) and (B, 5) of crosspoint circuit 31 are on) is established.

■After that, when the extension loop detector 28 corresponding to the 5M1 telephone handset 512 sends information that the 5th telephone handset 512 has gone on-hook to the control circuit 16, the control circuit 16 transmits the information to the hold circuit of the crosspoint circuit 31. As mentioned above, the cross points (A, 6), (C, O) to (C, 5) between the on-hold party and the hold signal generator 24 are turned off, and the cross points (A, 6), (C, O) to (C, 5) between the on-hold party and the above-mentioned transfer destination are turned off. Cross point with Episode 1M1 child fil12 (A, l) or (B, l) and (B
, O) to (B, 5) are turned on, and the external call after transfer [(A, 1) turned on] and the internal call [(B.

1) and (B, 2) to (B, 5) on] and establish a door-to-door call [(B, 1) and (B, 0) on] state.

■On the other hand, the transfer source's fifth telephone handset 512 does not go on-hook and the transfer destination's first telephone handset 512 does not go on-hook. When the Li handset 112 performs an "8" dial link (unsecure dialing), the extension loop detector 28 corresponding to the mlnf handset 112 sends this dial information to the control circuit 16. As a result, the control circuit 16 connects the hold partner and the hold signal generator 2 that are in the on state on the hold circuit of the crosspoint circuit 31 as described above.
Cross point with 4 (A, 6), (C, O) ~ (
C.

5) Turn off and call the number 1 handset 1 of the person on hold and the transfer destination above.
Cross point (A, 1), (A, 5) or (B, l) between 12 and the 5th telephone 512 which is the hold transfer source,
Turn on (B, 5) and CB,
, l), (A, 5) turned on], extension 3-way call [(B
, 1), (B, 5), and (B,

Note that the hold status of external calls, internal calls, and doorbell calls obtained by dialing 0" on the fifth telephone handset 512 can be canceled by dialing "0" again on the fifth telephone handset 512 before transfer. be done.

(Holding - Simultaneous Transfer...See Figure 7) When any telephone handset 12, for example, the first telephone handset i12, is in an outside line call, internal call, or doorbell call state, the first telephone handset i1
2 is dialed "0", the corresponding extension loop detector 28 sends this dial information to the control circuit 16, and the control circuit 16 dials the corresponding crosspoint (A, 6) on the hold circuit of the crosspoint circuit 31, (C,O)～(C,S
) is turned on to send the hold melody from the hold signal generator 24 to the person on hold who was in a conversation with the first telephone handset i12, and the crosspoint circuit 31 which was in the on state (A , i) or (B, i
) is turned off (on hold), the control circuit 16 turns on/off (D, i) of the cross point circuit 31, and sends an extension tone to the 12th talk handset i12.

Next, the m-th telephone handset i l 2 dials 9” (
- General call dialing) Then, the extension loop detector 28 corresponding to the m-th telephone handset i12 sends this dial information to the control circuit 16. As a result, the control circuit 16
Relay r1 of telephone handset 12 other than m-th telephone handset m12
3 to r53 to the calling signal oscillator 26, and relay r1
4 to r54 are switched to the off-hook detector 27, and - general paging is performed. At this time.

The control circuit 16 causes the on-hook telephone a12 to ring, and the off-hook telephone a! For j12, turn on/off the cross point (D, j) of the cross point circuit 31.
Turn it off, add an interrupt sound, and turn this off footer phone fi1
Sounds when 2 goes on hook. The control circuit 16 is
On-hook/off-hook information is obtained from the off-hook detector 27 corresponding to all the ringing on-footer telephone slave units 12, and it is monitored whether there is a response.

When the m-th telephone handset m12 first responds to the general paging by going off-hook, this off-hook information is transferred from the off-hook detector m27 to the control circuit 16. The control circuit 16 includes a relay rm3.corresponding to the m-th telephone handset m12.
rm4 is restored, the m-th telephone handset m12 stops ringing, and the cross points (B, j) and (B, m) of the cross-point circuit 31 are turned on, and the first telephone handset i
12 and the m-th telephone handset m12 are confirmed to be in a two-party conversation state.

Next, the control circuit 16 continues to ring the remaining telephone handsets 12 at once, and counts the number of rings. The control circuit 16 monitors whether there is a response within a preset number of ringings (for example, 5 times). If any one or more telephone handsets 12 respond by going off-hook within the set number of rings, the control circuit 16 will control the off-hook telephone charge 12.
(For example, relays r13 and r14 corresponding to telephone charge 1
is restored, and the corresponding crosspoint (B, k) of the crosspoint circuit 31 is turned on. As a result, the i'ltt telephone handset, the mth telephone handset, the third telephone handset...
are simultaneously connected via the crosspoint circuit 31, and a multi-extension call state with three, four, and so on is established.

Note that for the telephone handset 12 that has not been off-hook within the set number of rings, the control circuit 16 switches the corresponding relay r13. Restore r14 and stop ringing.

Next, when the first telephone handset 112 that is the transfer source goes on-hook, the control circuit 16 receives this on-hook information from the corresponding extension loop detector 28 and transfers the on-hook information to the cross-point circuit 31.
The cross point (A, 6
), (c, o) to (C,,5) are turned off, and two or more m-th telephone handsets of the holding party and the above-mentioned transfer destination are turned off,
Second, turn on the cross point with the telephone cordless handset at the same time.
Cross point (B, m), (B, k)...
, and establish a multiparty call status after transfer. That is, ■ establish an external multi-party call state after transferring the cross points (A, m), (A, k), etc. to the Y server at the same time, and then transfer the cross points (B, m), (B

k)...and (B,

m), (B, k), . . . and (B, O) are turned on at the same time to establish a multi-party intercom call state after transfer.

On the other hand, the first telephone handset i12, which is the transfer source, does not go on-hook, and the mth telephone handset, which is the transfer destination, and the first telephone handset, etc., are "8".
When dialing (unsecure dialing), the extension loop detectors m28, k28 corresponding to the m-th telephone handset, the m-th telephone handset, etc. transfer this dial information to the control circuit 16. As a result, the control circuit 16 connects the hold circuit of the cross point circuit 31 to the cross point (
A.

6), (C, O) to (C, 5) are turned off, and the held party and the second or more mTj of the above-mentioned transfer destination, handset,
Turn on the cross points of the th telephone handset and the i-th telephone handset of the hold transfer source at the same time, cross points (B, m),
(B, k)... is turned off to establish a multiparty call state after transfer. In other words, ■ cross point (A, i), (A
, m), (A, k)... at the same time to establish an external multi-party call status after transfer, and then turn on ■Crosspoint (B).

i), (B, m), CB, k) -... and (B,
x) at the same time to confirm the extension multi-party call status after transfer, and cross points (B, i) and (B).

m), (B, k), . . . and (B, O) are turned on at the same time to establish an extension door intercom multi-party call state after transfer.

Next, the operation of the above embodiment will be explained.

According to the above embodiment, when the telephone handset 12 performs a hold operation for a call during a call with a central office line, another telephone handset 12, or door intercom 13, Alternatively, the holding melody is sent to the doorphone 13, and the holding source telephone 12 performs a transfer operation to transfer the held station line, another telephone handset 12, or the doorphone 13 to another new telephone handset 4. '112 is the turning point. At this time, if the transfer destination telephone handset 12 performs a deprivation operation,
The phone a12 that is the hold transfer source can also participate in the call after the transfer.

In other words, the transfer destination party can select whether or not to keep the call confidential to the hold transfer source after the call has been transferred to hold. It is possible to easily realize multi-party calls including:

[Effect of the invention] As shown above, the final result is 1! According to $1, the transferred caller can choose whether or not to keep the call confidential to the hold transfer source, and the call will be held based on the transferred caller's intention to release the confidentiality. Multi-party calls including the transfer source can be easily realized.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a telephone device according to an embodiment of the present invention, FIG. 2 is a flowchart corresponding to the outside line calling mode, FIG. 3 is a flowchart corresponding to the outside line receiving mode, and FIG. 4 is an internal line calling mode. 5 is a flowchart corresponding to the intercom call mode, FIG. 6 is a flowchart corresponding to the hold transfer mode, and FIG. 7 is a flowchart corresponding to the hold-all transfer mode. DESCRIPTION OF SYMBOLS 10... Telephone device, 12... Telephone handset, 13... Door phone, 15... Main telephone circuit, 16... Control circuit, 18A, 18B... Office line, 19A, 198.2OA , 20B...Telephone line, 24.
...Melody IC (hold signal generator), 31...Cross point circuit (exchange circuit section). Patent applicant: Sekisui Chemical Co., Ltd. Representative Hiroshi 1) Iwakan Figure 2 Figure 3 Figure 4 Figure 5 Figure 6

Claims (1)

[Claims] (1) A telephone comprising a main telephone circuit connected to a central office line, a plurality of telephone handsets each connected to the main telephone circuit via telephone lines, and a control circuit that drives and controls the main telephone circuit. The main telephone circuit is equipped with a hold signal generator, and has an exchange connection between the office line and the handset, an exchange connection between the handsets, and an exchange connection between the handset and the hold signal generator. [1] When a call handset performs a hold operation for a call during an extension call with another call handset, the control circuit sends a hold signal to the other call handset that has been put on hold. A generator is connected to send a hold signal, and [2] when the hold source handset performs a transfer operation to another new call handset, it generates a ring tone to the transfer destination handset and sends a ringing signal. After establishing a call status between the forwarding destination handset and the holding source phone handset according to the above, [3] the transfer destination handset and the holding handset perform a de-privacy operation. A telephone device having a hold transfer function that controls the switching circuit unit to connect the holding source telephone handset and the other call handset on hold.