Power-failure resistant communication system

A communication system for connecting a terminal through a communication channel for a communication signal and a control channel for said control signal, comprising:

• a dialer for generating a push button signal at the time of a current supply;
• a switch for selecting a kind of dial signal to be generated from said dialer when a power failure occurs, out of the push button signal and a dial pulse signal;
• a receiver for receiving the push button signal generated from said dialer;
• and
• an external line interface for transmitting a dial signal according to an output of said receiver received through said control channel, to an external line at the time of a current supply,
• wherein when a power failure occurs, the dial signal of the kind selected by said switch, generated from said dialer is transmitted to said external line without passing through said receiver.

A communication apparatus which is connected to an external line through a private network, comprising:

• generating means for generating a dial signal;
• first setting means for setting a kind of dial signal that is generated from said generating means during a power failure;
• second setting means for setting a kind of dial signal so that said generating means generates a push button signal irrespective of a setting by said first setting means during a current supply;
• decoding means for decoding the push button signal generated by said generating means;
• first transmitting means for transmitting an output of said decoding means to a controller of said private network;
• and
• second transmitting means for transmitting the dial signal of the kind set by said first setting means, generated from said generating means to said external line without passing through said controller at the time of a power failure.

A communication apparatus comprising:

• dialing means for generating a dial signal;
• selecting means for selecting dial signals out of a push button signal and a dial pulse signal, and outputting a selection output representing selected dial signals;
• and
• setting means for setting a state of the selection output in a case of power supply,
• wherein said dialing means generates the dial signals selected by said selecting means in a case of power failure, and generates the dial signals dependent upon the state of the selection output set by said setting means and independent from the dial signals selected by said selecting means in the case of power supply.

A communication system comprising:

• dialing means for generating a dial signal;
• selecting means for selecting dial signals out of a push button signal and a dial pulse signal, for the time of power supply and for the time of power failure independently;
• internal network for connecting communicating means to an external line;
• detecting means for detecting the dial signal from said dialing means;
• transmitting means for transmitting a dial signal to the external line according to an output of said detecting means;
• and
• connecting means for connecting said dialing means to the external line without passing through said internal network at the time of power failure.

A control method for a dialer, comprising the steps of:

• inputting a selecting output from a switch for selecting a dial signal of the dialer out of a push button signal and a dial pulse signal;
• setting a state of the selection output during power supply;
• generating the dial signal dependent upon the selection output from the switch for selecting the dial signal during power failure;
• and
• generating the dial signal dependent upon the selection output set in said setting step during the power supply and independent from the switch for selecting the dial signal.