CA1049671A
(en )
1979-02-27
Key telephone system intercom arrangement
GB732028A
(cg-RX-API-DMAC10.html )
US3872262A
(en )
1975-03-18
Key telephone system
US3150238A
(en )
1964-09-22
Relay control circuit
US3321580A
(en )
1967-05-23
Hands-free communication systems including privacy features
US3703611A
(en )
1972-11-21
Telephone system
JPS5772452A
(en )
1982-05-06
Telephone set with speaker receiving function
US2815398A
(en )
1957-12-03
Intercommunication systems
US1932647A
(en )
1933-10-31
Telephone instrument
GB1050744A
(cg-RX-API-DMAC10.html )
US2060250A
(en )
1936-11-10
Combined teleprinter and telephone system
JPS5999896A
(ja )
1984-06-08
電話装置における送出信号確認方式
GB736988A
(en )
1955-09-14
Improvements in or relating to loudspeaking telephone systems
GB770937A
(en )
1957-03-27
Improvements in or relating to loudspeaker intercommunicating systems
JPS61212194A
(ja )
1986-09-20
ボタン電話装置
JP2561456B2
(ja )
1996-12-11
ボタン電話装置
GB776588A
(cg-RX-API-DMAC10.html )
GB677894A
(en )
1952-08-27
Improvements in or relating to intercommunication telephone systems
JPS5787657A
(en )
1982-06-01
Loudspeaker telephone system
JPS61107852A
(ja )
1986-05-26
電話転送装置を用いた三者通話に於る回線制御方法
US2727948A
(en )
1955-12-20
Discriminating link circuit
GB701947A
(cg-RX-API-DMAC10.html )
US1954932A
(en )
1934-04-17
Telephone and direct conversation circuits
JPS63309091A
(ja )
1988-12-16
長距離内線付加装置
JPS56166695A
(en )
1981-12-21
Incoming call answering system